Mammography Screening: The Great Hoax

By Peter C. Gøtzsche – Unbekoming Book Summary

A famous surgeon who was my father's mate, my father was a doctor, told me many times never to go for "routine" check of any kind. He said " you go for a check when you ARE sick, before it is not only useless, it is dangerous. Too many of the checks they do are dangerous." – Niki

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Once the penny dropped for me that the whole cancer industrial complex was a deadly wealth transferring fraud, it become easier to see the host of moving parts that make up the bigger construction.

Screening is a most important part of the hoax/fraud.

Screening is simply new business generation.

For the predatory monster that is Cartel Medicine needs to feed, and it has a special taste for women.

I wrote about the excellent Boobs documentary here in my Mammogram stack.

If you haven’t seen that documentary, I highly recommend it.

It was this tweet by Gøtzsche that prompted this stack.

Mammography screening: The greatest hoax. Read the update of my 2012 book for free: https://bit.ly/3Cvobip Breast screening has been sold to the public with the message that it saves lives and breasts. It does neither. Mammography screening is harmful and should be stopped.

I hadn’t realised he had written a whole book on the subject let alone updated it.

So here we are.

With thanks to Peter Gøtzsche.

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Let’s start with an analogy.

Analogy

Imagine you're at a busy airport, and there's a new security system that promises to catch potential threats more effectively than ever before. The airport authorities are excited about this system and encourage everyone to go through it, claiming it will make air travel much safer.

However, upon closer inspection, you discover some troubling facts:

1. The new system doesn't actually reduce the overall number of incidents on flights. (This is like screening not reducing overall mortality.)

2. For every real threat it catches, it flags 10 innocent travelers as suspicious. These people are subjected to intensive questioning, additional searches, and some even miss their flights. (This represents overdiagnosis and false positives.)

3. Some of the flagged travelers are told they can't fly unless they undergo invasive procedures, even though many of them were never actually a threat. (This is like overtreatment, including unnecessary mastectomies.)

4. The system is particularly bad at catching the most dangerous threats, which still slip through at about the same rate as before. (This is like screening not reducing advanced cancers.)

5. Despite these issues, the airport continues to promote the system, using statistics that make it look more effective than it really is. They emphasize the few genuine threats caught but downplay the many innocent travelers who were wrongly flagged.

6. When some security experts point out these problems, they face harsh criticism and accusations of endangering passenger safety. (This represents the challenges faced by researchers critical of screening.)

7. Meanwhile, other improvements in air travel safety, like better pilot training and aircraft maintenance, are making flying safer regardless of this new security system. (This is like improved treatments and awareness reducing breast cancer mortality independently of screening.)

In this analogy, the new airport security system is like mammography screening. While it's promoted as a life-saving measure, closer examination reveals that it causes significant harm and disruption while providing little proven benefit. Just as travelers deserve to know the true effects of a security system, women deserve accurate information about the benefits and harms of mammography screening to make informed decisions about their health.

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For those that don’t want to read the longer Q&A summary of the book, here is something shorter.

12-point summary of the book:

1. Mammography screening does not reduce overall mortality. The best studies show that women who get screened have about the same chance of dying as those who don't, from any cause. The relative risk for all-cause mortality in well-conducted trials is 1.01 (95% CI 0.99 to 1.04), meaning there's no significant difference. This suggests that even if screening prevents some breast cancer deaths, it might lead to other health problems that balance out any benefit.

2. There is no reliable evidence that screening reduces breast cancer mortality. When we look at the most trustworthy studies, the reduction in breast cancer deaths is small and could be due to chance. The relative risk for breast cancer mortality is 0.93 (95% CI 0.80 to 1.09) after 13 years, meaning it could range from a 20% reduction to a 9% increase. This uncertainty challenges the core justification for mammography screening programs.

3. Overdiagnosis is a major harm of screening, affecting about one in three screen-detected breast cancers. This means finding cancers that would never have caused symptoms or death if left undetected. Estimates range from 30% in randomized trials to 52% in organized screening programs. Overdiagnosis leads to unnecessary treatment, including surgery, radiation, and chemotherapy, causing physical and psychological harm to healthy women.

4. Screening increases the number of mastectomies by about 20%, contrary to claims that it leads to less aggressive treatment. In the UK, there was a 36% increase in mastectomies for invasive cancer and a 422% increase for ductal carcinoma in situ (DCIS) from 1990 to 2001 after screening was introduced. This increase is largely due to the detection of slow-growing cancers and DCIS that might never have caused problems.

5. False positives are common in mammography screening, affecting 25% of women in the UK and 50% in the USA over 10 screening rounds. A false positive is when a mammogram suggests cancer might be present, but further tests show it isn't. These false alarms can cause significant anxiety, additional invasive tests, and long-lasting psychological distress, impacting women's quality of life and attitudes towards future screening.

6. Screening has not reduced the incidence of advanced cancers as expected. If screening were effective, we should see fewer late-stage cancers being diagnosed. However, studies in multiple countries have shown no significant decrease in late-stage cancers following the introduction of screening programs. This suggests that screening might not be preventing cancer progression as intended.

7. The claimed benefits of screening are often exaggerated in both scientific literature and public communication. Some studies have inflated the benefit-to-harm ratio by up to 25 times, often by underestimating harms like overdiagnosis or using flawed statistical methods. This exaggeration has led to overly optimistic views about the effectiveness of screening among both the public and healthcare professionals.

8. The lead time for breast cancer - how much earlier screening detects cancer compared to symptoms - is much shorter than often assumed, likely less than one year rather than 2-5 years as commonly stated. This shorter lead time means that the window of opportunity for screening to make a difference is smaller than previously thought, which could explain why screening hasn't shown clear benefits in reducing mortality.

9. Informed consent is often lacking in screening programs. Many invitations and informational materials fail to mention overdiagnosis or present balanced information about both benefits and harms. This lack of comprehensive information makes it difficult for women to make truly informed decisions about participating in screening, raising ethical concerns about these programs.

10. Conflicts of interest have significantly influenced screening research and policy. Many proponents of screening have financial or professional interests in its continuation, such as radiologists who perform mammograms or organizations that receive funding for screening programs. These conflicts can lead to biased interpretations of data and resistance to evidence that questions the value of screening.

11. The total cost of screening can be substantial, raising questions about resource allocation in healthcare. In the USA, screening women in their 40s costs $2 billion per year. Given the uncertain benefits and known harms of screening, this level of expenditure is controversial. Some argue these resources could be better spent on other health interventions or on improving breast cancer treatment.

12. Breast cancer awareness and improved treatments likely account for much of the observed decrease in breast cancer mortality, rather than screening. Mortality has decreased similarly in non-screened age groups and in countries without screening programs. This suggests that factors such as better therapies, faster diagnosis of symptomatic cancers, and increased awareness of breast health may be more important in reducing breast cancer deaths than mammography screening.

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Mammography screening: The great hoax

By Peter C. Gøtzsche

Mammography Screening The Great Hoax

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39 Questions & Answers

Question 1: What are the main findings of randomized trials on mammography screening for breast cancer?

The randomized trials on mammography screening have produced conflicting results. The most reliable trials, those with adequate randomization, did not show a significant reduction in breast cancer mortality. These trials found a relative risk of 0.93 (95% confidence interval 0.80 to 1.09) after 13 years. The trials with suboptimal randomization showed a more favorable effect, with a relative risk of 0.75 (0.67 to 0.83).

Importantly, none of the trials showed a reduction in total cancer mortality or all-cause mortality. The relative risk for total cancer mortality, including breast cancer, was 1.02 (95% CI 0.95 to 1.10) after 10 years in the adequately randomized trials. This suggests that even if screening reduces breast cancer mortality, it may increase mortality from other causes, possibly due to overdiagnosis and overtreatment.

Question 2: How is overdiagnosis defined in the context of breast cancer screening, and what are its consequences?

Overdiagnosis in breast cancer screening refers to the detection of cancers that would never have caused symptoms or problems in a woman's remaining lifetime. These are cancers that would not have been discovered without screening. The consequence is that healthy women are unnecessarily turned into cancer patients and subjected to treatments they don't need.

The consequences of overdiagnosis are significant. Overdiagnosed women undergo unnecessary surgery, radiotherapy, and sometimes chemotherapy. These treatments can have serious side effects, including an increased risk of heart disease from radiotherapy. Overdiagnosis also causes psychological harm, as women live with the knowledge of a cancer diagnosis that would never have affected them. Estimates of overdiagnosis vary, but some studies suggest it affects up to one-third of screen-detected breast cancers.

Question 3: What are the primary harms associated with mammography screening?

The primary harms associated with mammography screening are overdiagnosis, overtreatment, false positive results, and psychological distress. Overdiagnosis leads to unnecessary treatment, including surgery, radiotherapy, and chemotherapy, which can have serious side effects. Some healthy women who are overdiagnosed will die from their treatment.

False positive results are common, affecting about 25% of screened women (50% in the USA) over 10 screening rounds. These lead to unnecessary anxiety and additional invasive procedures. The psychological impact of false positives can be long-lasting, with many women experiencing significant distress for years after a false positive result. Additionally, screening increases the overall number of mastectomies performed, contrary to claims that it reduces aggressive treatments.

Question 4: How do the benefits of mammography screening compare to its harms?

The comparison of benefits and harms of mammography screening is controversial, with different studies producing widely varying estimates. According to the most reliable randomized trials, there is no significant reduction in breast cancer mortality from screening. Even studies claiming a benefit typically estimate that one breast cancer death is avoided for every 10 women overdiagnosed and overtreated.

The harms are substantial and affect many more women than any potential benefits. For every 2000 women invited for screening over 10 years, one may avoid dying from breast cancer. However, 10 healthy women will be overdiagnosed and treated unnecessarily, and about 200 women will experience false positive results. When considering the lack of effect on total mortality and the increased number of mastectomies due to screening, the harms appear to outweigh the benefits.

Question 5: What controversies surround the Cochrane reviews on mammography screening?

The Cochrane reviews on mammography screening have been at the center of significant controversy. The first Cochrane review in 2001 faced severe editorial interference from the Cochrane Breast Cancer Group, which refused to allow the publication of data on the harms of screening, particularly overdiagnosis and overtreatment. This led to the full review being published in The Lancet instead.

The controversy continued with subsequent updates of the review. The Cochrane editors insisted on combining results from all trials, despite clear differences in quality and results between adequately and inadequately randomized trials. This led to disputes over the appropriate presentation of the data and interpretation of the results. The review process was repeatedly delayed, with the authors facing accusations of bias and attempts to censor their work. These controversies highlighted tensions between maintaining scientific integrity and managing the political sensitivities surrounding mammography screening.

Question 6: How have critiques of mammography screening research evolved over time?

Critiques of mammography screening research have become more sophisticated and comprehensive over time. Initially, criticisms focused on methodological issues in individual trials, such as problems with randomization in the Swedish Two-County trial. As more data accumulated, critiques expanded to include systematic reviews and meta-analyses of multiple trials.

Later critiques began to focus more on the interpretation of results, highlighting issues such as lead time bias, length bias, and the problem of overdiagnosis. There has been increased attention to the discrepancy between reductions in breast cancer mortality and the lack of effect on total mortality. More recent critiques have also addressed the applicability of older trial results to current practice, given improvements in treatment and increased breast cancer awareness. Additionally, there has been growing criticism of the use of observational studies and modeling to support screening, with calls for more focus on randomized trial evidence.

Question 7: What are the key points of debate in the mammography screening controversy?

The mammography screening controversy centers on several key points of debate. One major issue is the magnitude of benefit, if any, from screening. While some studies claim significant reductions in breast cancer mortality, others argue that there is no reliable evidence of benefit when considering only the highest quality trials.

Another crucial debate is about overdiagnosis and overtreatment. There is disagreement over the extent of overdiagnosis, with estimates ranging from a few percent to over 50% of screen-detected cancers. The balance of benefits and harms is hotly contested, with some arguing that the harms outweigh any potential benefits.

The appropriate age range for screening and the screening interval are also debated. There's particular controversy over screening women under 50 and over 70. The validity of using breast cancer mortality as an outcome measure, rather than all-cause mortality, is another point of contention. Finally, there are debates about the ethics of population screening programs and whether they allow for truly informed consent.

Question 8: How has the concept of informed consent been applied to mammography screening?

The application of informed consent to mammography screening has been problematic. Studies of invitations to screening programs and informational materials provided to women have found that they often present an overly positive view of screening, emphasizing benefits while downplaying or omitting information about harms.

Many invitations fail to mention overdiagnosis, one of the most serious harms of screening. When harms are mentioned, they are often presented in a way that minimizes their importance. For example, the risk of a false positive result might be given for a single screening round rather than the cumulative risk over multiple rounds.

There have been calls for more balanced information to be provided to women, allowing for truly informed decision-making. However, there is resistance to this from some screening advocates who fear it might reduce participation rates. The tension between promoting uptake of screening and ensuring informed consent remains unresolved in many screening programs.

Question 9: How have public health policies on breast cancer screening changed in response to new evidence?

Public health policies on breast cancer screening have been slow to change in response to new evidence. Despite mounting evidence of harms and questionable benefits, many countries have maintained or even expanded their screening programs. However, there have been some shifts in recent years.

In some countries, there has been a move towards providing more balanced information to women about the potential benefits and harms of screening. For example, the UK revised its screening invitation leaflets to include information about overdiagnosis, although critics argue these revisions don't go far enough.

There have also been changes in age recommendations in some places. For instance, the US Preventive Services Task Force revised its guidelines in 2009 to recommend against routine screening for women aged 40-49, sparking considerable controversy. Some countries have also begun to consider more personalized approaches to screening based on individual risk factors. However, overall, there has been significant inertia in policy changes, often attributed to political pressures and vested interests in maintaining existing programs.

Question 10: What statistical methods are used to analyze mammography screening data, and what are their limitations?

Various statistical methods are used to analyze mammography screening data, each with its own limitations. Randomized controlled trials typically use intention-to-treat analysis, comparing outcomes between invited and non-invited groups. However, this can underestimate the effect of screening if many invited women don't attend. Some researchers use methods to estimate the effect among those who actually attend screening, but these can introduce bias.

For observational studies, methods like age-period-cohort models are often used to separate the effects of screening from other factors affecting breast cancer rates. However, these models rely on assumptions that may not hold true. Case-control studies have been used but are prone to several biases, including self-selection bias.

Modeling studies are frequently used to estimate long-term effects of screening, but these are highly dependent on the assumptions built into the models. A major limitation across many analyses is the focus on relative risk reductions rather than absolute risk reductions, which can make benefits appear larger than they are. Additionally, analyses often fail to adequately account for lead time bias and length bias, potentially overestimating screening benefits.

Question 11: How do lead time bias and length bias affect the interpretation of screening trial results?

Lead time bias occurs when screening detects a cancer earlier than it would have been diagnosed clinically, but without actually changing the course of the disease. This can make survival times appear longer even if the actual date of death remains unchanged. Length bias refers to the tendency of screening to detect slow-growing, less aggressive cancers that are less likely to be fatal.

These biases can significantly distort the apparent benefits of screening. They can make it appear that screening improves survival rates even if it doesn't actually extend lives. For example, five-year survival rates often look better with screening due to lead time bias, even if there's no reduction in mortality. Length bias can make screen-detected cancers appear to have a better prognosis, even if screening isn't actually saving lives.

To avoid these biases, it's crucial to focus on mortality rates rather than survival rates, and to have adequate follow-up time in screening trials. However, even mortality data can be affected if cause of death is not accurately determined.

Question 12: What trends have been observed in breast cancer mortality rates in countries with and without screening programs?

Trends in breast cancer mortality rates have been similar in many countries, regardless of whether they have implemented screening programs. In general, breast cancer mortality has been declining since the 1990s in most developed countries. However, this decline began before screening could have had an effect in most places and has been observed in non-screened age groups as well.

For example, in Denmark, where screening was implemented in only 20% of the country for many years, the decline in breast cancer mortality was similar in screened and non-screened areas. In fact, the largest declines were often seen in women under 50, who were generally not invited to screening.

These trends suggest that factors other than screening, such as improved treatment and increased breast cancer awareness, are likely responsible for much of the observed mortality reduction. The similarity in trends between screened and unscreened populations casts doubt on the effectiveness of mammography screening programs.

Question 13: Why is total mortality an important outcome measure in screening trials?

Total mortality is considered the most important and reliable outcome measure in screening trials for several reasons. First, it avoids the problem of misclassification of cause of death, which can bias results in favor of screening when only breast cancer mortality is considered. Even with blinded endpoint committees, it's often difficult to determine whether a death was due to breast cancer or other causes, particularly in older women with multiple health issues.

Second, total mortality captures any potential negative effects of screening, such as deaths from overdiagnosis and overtreatment. Some overdiagnosed women may die from the side effects of unnecessary treatment, such as radiotherapy-induced heart disease.

Third, total mortality provides a clear picture of the overall impact of screening on women's lives. If screening reduces breast cancer deaths but increases deaths from other causes, there's no net benefit to women. Importantly, none of the mammography screening trials have shown a reduction in total mortality, which casts doubt on the overall effectiveness of screening.

Question 14: How has the incidence of advanced breast cancer been affected by screening programs?

Contrary to expectations, screening programs have generally not led to a significant reduction in the incidence of advanced breast cancers. If screening were effective, one would expect to see a decrease in late-stage cancers as more cancers are detected early. However, this has not been consistently observed.

Several studies, including those from the Netherlands, Norway, and Denmark, have found that the introduction of screening programs did not lead to a decrease in the incidence of advanced breast cancers. In some cases, there was even a slight increase. For example, a study in Norway found that the incidence of late-stage breast cancer was stable or even increased slightly after the introduction of screening.

This lack of reduction in advanced cancers suggests that screening may not be preventing progression to advanced disease as intended. It also supports the idea that many screen-detected cancers may be overdiagnosed – representing lesions that would not have progressed to clinically significant disease in a woman's lifetime.

Question 15: What impact does mammography screening have on quality of life?

Mammography screening can have both positive and negative impacts on quality of life. For some women, regular screening may provide reassurance and a sense of taking control of their health. However, the negative impacts are often underappreciated and can be substantial.

False positive results, which affect a large proportion of screened women, can cause significant anxiety and psychological distress. This distress can persist for years after the false positive result. Overdiagnosis and overtreatment can have severe impacts on quality of life. Women who are overdiagnosed experience the trauma of a cancer diagnosis and undergo unnecessary treatments, which can have long-term side effects.

Even true positive results can negatively impact quality of life if they detect cancers that would not have caused symptoms in a woman's lifetime. Studies have shown that two to three years after breast cancer treatment, 47% of women reported chronic pain, often several times a week. When considering these factors, some analyses suggest that the overall impact of screening on quality of life may be negative, even under optimistic assumptions about its effectiveness.

Question 16: What are the rates and consequences of false positive results in mammography?

False positive results are a common occurrence in mammography screening. In the UK, at least 25% of women will experience a false positive result over 10 screening rounds. In the USA, this figure is even higher, at about 50%. These false positives lead to additional testing, including further imaging and often biopsies, which can be invasive and cause anxiety.

The psychological consequences of false positives can be severe and long-lasting. Many women experience significant anxiety and distress upon receiving a positive result, and this distress can persist even after the result is confirmed to be false. Studies have shown that some women continue to experience psychological harm years after a false positive result.

False positives also lead to unnecessary medical procedures. In the UK, about 3% of women recalled after screening will have a surgical biopsy for what turns out to be a false positive result. These procedures carry their own risks and can lead to complications. The high rate of false positives is one of the major drawbacks of mammography screening and contributes significantly to its potential harms.

Question 17: How have mastectomy rates changed with the introduction of screening programs?

Contrary to claims that screening reduces the need for aggressive treatment, the introduction of screening programs has generally led to an increase in mastectomy rates. This increase is largely due to overdiagnosis and the detection of ductal carcinoma in situ (DCIS), which is often treated with mastectomy.

In Denmark, for example, there was a significant increase in mastectomies when screening was introduced in Copenhagen and Fyn. This increase was not followed by later declines, and the overall trend in mastectomies was similar in screened and non-screened areas. In the UK, there was a 36% increase in mastectomies for invasive cancer and a 422% increase for DCIS from 1990 to 2001, following the introduction of screening.

The increase in mastectomies is particularly pronounced for DCIS, which is rarely detected without screening. In the UK, 29% of DCIS lesions are treated with mastectomy, compared with 26% of invasive cancers. This contradicts the common claim that screening leads to less aggressive treatment and breast conservation.

Question 18: What are the potential harms of radiotherapy and chemotherapy resulting from overdiagnosis?

Radiotherapy and chemotherapy resulting from overdiagnosis can lead to significant harms. These treatments are often given to women who have been diagnosed with breast cancer through screening, including those who are overdiagnosed – meaning their cancer would never have caused symptoms or death if left undetected.

Radiotherapy can increase the risk of heart disease and lung cancer. A study found that radiotherapy increases deaths from heart disease by 27%. This is particularly concerning for overdiagnosed women, as they receive no benefit from the treatment to offset these risks. Chemotherapy can cause a range of short-term and long-term side effects, including fatigue, nausea, hair loss, and in some cases, permanent organ damage or secondary cancers.

Both treatments can significantly impact quality of life. Many women experience chronic pain and other long-term effects from these treatments. For overdiagnosed women, these harms are entirely unnecessary, as their cancer would never have threatened their health. The potential for these severe side effects in women who don't actually need treatment is a major argument against widespread mammography screening.

Question 19: How cost-effective are mammography screening programs?

The cost-effectiveness of mammography screening programs is highly debatable and depends greatly on the assumptions made about the benefits and harms of screening. Early estimates of cost-effectiveness were often based on optimistic assumptions about the mortality reduction from screening and didn't fully account for the costs associated with overdiagnosis and overtreatment.

More recent analyses, taking into account the limited mortality benefit and the substantial harms of screening, suggest that mammography screening may not be cost-effective. The costs include not only the direct expenses of the screening program itself, but also the downstream costs of additional testing, biopsies, and treatment for both true and false positive results.

In the United States, a recent analysis showed that the total national cost of screening women in their 40s was $2 billion per year. Given the questionable benefits and significant harms, particularly for younger women, this level of expenditure is hard to justify. Some researchers argue that these resources could be better spent on other public health interventions or on improving breast cancer treatment.

Question 20: What criticisms have been made of the NHS Breast Screening Programme in the UK?

The NHS Breast Screening Programme in the UK has faced numerous criticisms. One major criticism is that the program has consistently overstated the benefits of screening while downplaying or ignoring the harms. The information provided to women invited for screening has been criticized for not allowing truly informed consent, as it often fails to mention overdiagnosis or presents an overly optimistic view of the screening's effectiveness.

Another criticism is that the program has been slow to respond to new evidence questioning the value of screening. Despite mounting evidence of limited benefit and substantial harm, the program has continued to expand, including extending the age range for screening.

The program has also been criticized for its lack of transparency and its resistance to independent evaluation. When an independent review (the Marmot review) was finally conducted in 2012, it was criticized for using outdated methods and for reaching conclusions that weren't supported by the data presented.

Finally, there have been concerns about the program's cost-effectiveness, with some arguing that the resources could be better spent on other health interventions. Critics argue that the program has become entrenched due to political and institutional inertia, rather than because of clear evidence of benefit.

Question 21: What role has the Nordic Cochrane Centre played in the mammography screening debate?

The Nordic Cochrane Centre, particularly under the leadership of Peter C. Gøtzsche, has played a pivotal role in the mammography screening debate. They conducted some of the most comprehensive and critical reviews of the mammography screening trials, challenging the prevailing narrative about the benefits of screening. Their first Cochrane review in 2001 sparked significant controversy by concluding that there was no reliable evidence that screening reduced breast cancer mortality.

The Centre has consistently emphasized the harms of screening, particularly overdiagnosis, and has argued that these harms likely outweigh any potential benefits. They have also been critical of the information provided to women invited for screening, arguing that it often fails to present a balanced view of risks and benefits. The Centre's work has been influential in stimulating debate and encouraging a more critical evaluation of mammography screening programs worldwide.

Question 22: What are the main arguments presented in Peter C. Gøtzsche's research and books on mammography screening?

Peter C. Gøtzsche's research and books on mammography screening present several key arguments. Firstly, he argues that the benefits of mammography screening have been greatly exaggerated while the harms have been downplayed or ignored. Based on his analysis of the randomized trials, he concludes that screening does not reduce overall mortality and may not even reduce breast cancer mortality when only the most reliable trials are considered.

Secondly, Gøtzsche emphasizes the harm of overdiagnosis, estimating that it affects about one in three screen-detected breast cancers. He argues that this leads to unnecessary treatment, including surgery, radiotherapy, and chemotherapy, causing physical and psychological harm to many women. He also highlights the problem of false positives and the increased rate of mastectomies associated with screening. Overall, Gøtzsche contends that mammography screening does more harm than good and should be abandoned.

Question 23: How have conflicts of interest influenced mammography screening research and policy?

Conflicts of interest have significantly influenced mammography screening research and policy. Many of the researchers and policymakers involved in promoting screening have financial or professional interests in its continuation. For example, radiologists and cancer organizations often benefit from widespread screening programs. This can lead to biased interpretations of data and resistance to evidence that questions the value of screening.

These conflicts of interest have manifested in various ways, including the suppression of critical research, the promotion of flawed studies that support screening, and the development of guidelines that favor screening despite evidence of limited benefit. There have also been instances of researchers failing to disclose relevant conflicts of interest in published papers. These issues have made it difficult to have an objective, evidence-based debate about the merits of mammography screening.

Question 24: What challenges to academic freedom have arisen in the context of mammography screening research?

Research challenging the effectiveness of mammography screening has faced significant obstacles to academic freedom. Critics of screening have reported difficulties in publishing their work, facing hostile peer reviews and editorial decisions. In some cases, researchers have faced personal attacks and attempts to discredit their work, rather than engagement with their scientific arguments.

There have also been instances of institutional pressure to suppress or modify research findings that are unfavorable to screening. For example, the Nordic Cochrane Centre faced significant resistance when trying to publish their first review on mammography screening. Some researchers have reported threats to their funding or career prospects when they produced work critical of screening. These challenges have created an environment where it can be difficult to conduct and disseminate objective research on this controversial topic.

Question 25: How have medical journals handled the publication of controversial findings on mammography screening?

Medical journals have had a mixed record in handling controversial findings on mammography screening. Some journals, like The Lancet and BMJ, have published critical studies and fostered debate on the topic. However, there have also been instances of editorial bias and resistance to publishing findings that challenge the status quo on screening.

Some researchers have reported difficulties in getting critical studies published, facing unusually hostile peer reviews or editorial decisions that seem to be influenced by the controversial nature of the findings rather than their scientific merit. There have also been cases of journals retracting or refusing to publish letters critical of pro-screening studies. These issues have raised concerns about the objectivity of the peer review process and the role of journals in shaping the discourse on mammography screening.

Question 26: What are the key differences between the Swedish Two-County trial and other mammography screening trials?

The Swedish Two-County trial stands out from other mammography screening trials in several ways. It reported a much larger benefit from screening than most other trials, showing a 31% reduction in breast cancer mortality. However, this trial has been criticized for methodological flaws, including problems with randomization and blinding in the assessment of cause of death.

Unlike some other trials, the Two-County trial used a cluster randomization method, randomizing by geographical area rather than individual women. This approach is more prone to bias. The trial also had a particularly long screening interval and used single-view mammography, which differs from current practice in many countries. These factors, combined with concerns about data quality and inconsistencies in reported numbers, have led many researchers to question the reliability of this trial's results compared to other mammography screening trials.

Question 27: How have observational studies contributed to the understanding of mammography screening outcomes?

Observational studies have provided additional data on mammography screening outcomes in real-world settings, complementing the evidence from randomized trials. These studies have often been used to assess the long-term impacts of screening programs and to estimate overdiagnosis rates. However, their interpretation is complicated by the lack of a randomized control group and the potential for various biases.

Some observational studies have suggested larger benefits from screening than seen in the randomized trials, but these findings are often criticized for not adequately accounting for bias, particularly self-selection bias and lead time bias. Other observational studies have provided important insights into the harms of screening, including rates of false positives and overdiagnosis in routine screening programs. Overall, while observational studies have added to our understanding, their results must be interpreted cautiously due to their inherent limitations.

Question 28: What role does ductal carcinoma in situ (DCIS) play in the overdiagnosis debate?

Ductal carcinoma in situ (DCIS) plays a central role in the overdiagnosis debate. DCIS is a condition where abnormal cells are found in the milk ducts of the breast, but have not spread outside the ducts. It is rarely detected without screening but accounts for a significant proportion of screen-detected breast "cancers". However, most cases of DCIS would never progress to invasive cancer if left untreated.

The detection and treatment of DCIS contribute significantly to overdiagnosis and overtreatment in breast cancer screening. Despite being non-invasive, DCIS is often treated aggressively, including with mastectomy. This leads to many women undergoing unnecessary treatment for a condition that would never have threatened their health. The high rate of DCIS detection in screening programs, combined with uncertainty about which cases might progress to invasive cancer, makes it a key factor in the argument that screening causes more harm than good.

Question 29: How do tumor growth rates affect the effectiveness of mammography screening?

Tumor growth rates significantly impact the effectiveness of mammography screening. Breast cancers have widely varying growth rates, with doubling times ranging from about 70 days to over 4 years. This variability affects screening in several ways. Fast-growing, aggressive cancers may develop and spread between screening rounds, leading to interval cancers that are not detected by screening. On the other hand, very slow-growing cancers may be detected by screening but would never have caused symptoms in a woman's lifetime, contributing to overdiagnosis.

The heterogeneity of tumor growth rates means that screening is most likely to detect slow-growing cancers, which are less likely to be life-threatening (length bias). This can create a misleading impression of improved survival rates with screening, even if there's no actual benefit. Additionally, the long preclinical phase of many breast cancers (estimated at an average of 21 years) means that even cancers detected by screening have often been present for many years, challenging the notion of "early" detection.

Question 30: What impact has increased breast cancer awareness had on mortality rates?

Increased breast cancer awareness has likely had a significant impact on mortality rates, independent of screening programs. Greater awareness has led to women seeking medical attention more quickly when they notice breast changes, potentially leading to earlier diagnosis of symptomatic cancers. This can result in treatment at an earlier stage, which may improve outcomes.

Studies have shown that breast cancer mortality has declined similarly in age groups not invited to screening and in countries without national screening programs, suggesting factors other than screening are playing a major role. Increased awareness may also have contributed to lifestyle changes that reduce breast cancer risk. However, it's challenging to separate the effects of awareness from other factors like improved treatments. The impact of awareness highlights the importance of considering all factors, not just screening, when interpreting trends in breast cancer mortality.

Question 31: How have changes in breast cancer treatment affected the interpretation of screening trial results?

Changes in breast cancer treatment have significantly complicated the interpretation of screening trial results. Most randomized trials of mammography screening were conducted decades ago when treatment options were more limited. Since then, there have been major advances in breast cancer treatment, including improved surgical techniques, more effective chemotherapy regimens, and targeted therapies like hormone treatments and immunotherapies.

These improvements in treatment mean that the absolute benefit of early detection through screening is likely smaller now than it was when the trials were conducted. A cancer that might have been fatal if detected at a later stage in the past might now be successfully treated even if found later. This makes it challenging to apply the results of old trials to current practice and may mean that the benefits of screening have been overestimated in modern contexts.

Question 32: What ethical considerations are involved in population-based mammography screening programs?

Population-based mammography screening programs raise several ethical concerns. One key issue is the tension between public health goals and individual autonomy. While screening programs aim to reduce cancer mortality at a population level, they expose many healthy individuals to potential harms. This raises questions about the ethical justification for subjecting asymptomatic women to these risks.

Another major ethical consideration is informed consent. Many screening programs have been criticized for not providing women with balanced information about both benefits and harms, making truly informed decision-making difficult. There are also concerns about equity and resource allocation, as the high cost of screening programs may divert resources from other health interventions. Finally, the issue of overdiagnosis raises ethical questions about the harm of unnecessarily turning healthy women into cancer patients.

Question 33: How effective are current methods of communicating mammography screening risks and benefits to women?

Current methods of communicating mammography screening risks and benefits to women have often been found to be inadequate. Many invitations to screening and informational materials emphasize benefits while downplaying or omitting information about harms. Studies have shown that women often overestimate the benefits of screening and are unaware of potential harms like overdiagnosis.

The use of relative risk reductions rather than absolute risk reductions can make benefits appear larger than they are. There's also often a lack of clear information about the likelihood of false positives and their consequences. Some progress has been made in recent years, with some countries revising their informational materials to include more balanced information. However, there's still a long way to go in ensuring that women receive clear, unbiased information that allows for truly informed decision-making about participation in screening.

Question 34: What evidence exists regarding the effectiveness of breast self-examination and clinical breast examination?

The evidence regarding the effectiveness of breast self-examination (BSE) is not supportive of its use as a screening method. Randomized trials have shown that regular BSE does not reduce breast cancer mortality but does increase the number of biopsies performed. As a result, many organizations no longer recommend routine BSE as a screening method.

The evidence for clinical breast examination (CBE) is mixed. Some observational studies have suggested that CBE may be effective in detecting some cancers, particularly in younger women or in areas where mammography is not readily available. However, there's a lack of strong evidence from randomized trials showing that CBE reduces breast cancer mortality. The sensitivity of CBE is also lower than mammography. Given the uncertain benefits and potential for false positives, CBE is not typically recommended as a standalone screening method in countries where mammography is available.

Question 35: How do age and screening interval recommendations vary between different organizations and countries?

Age and screening interval recommendations for mammography vary significantly between different organizations and countries. In the United States, recommendations range from starting at age 40 (American Cancer Society) to age 50 (U.S. Preventive Services Task Force), with some recommending annual screening and others biennial. The UK National Health Service invites women aged 50-70 every three years, while some European countries screen women aged 50-69 every two years.

These variations reflect differences in interpreting the evidence, weighing benefits against harms, and considering cost-effectiveness. There's particular controversy around screening women under 50, where the benefit-to-harm ratio is less favorable. Some countries have also extended screening to older ages, despite limited evidence of benefit in this group. These differences in recommendations highlight the uncertainty in the evidence and the role of value judgments in screening policies.

Question 36: What role does breast density play in mammography screening effectiveness?

Breast density plays a significant role in mammography screening effectiveness. Dense breast tissue appears white on mammograms, as do potential tumors, making it more difficult to detect cancers in women with dense breasts. This can lead to more false negatives, where cancers are missed by screening. Studies have shown that mammography is less sensitive and specific in women with dense breasts.

Additionally, women with dense breasts have a higher risk of developing breast cancer, further complicating the screening picture. Some jurisdictions have passed laws requiring women to be informed of their breast density and the associated limitations of mammography. This has led to discussions about supplemental screening methods for women with dense breasts, such as ultrasound or MRI. However, while these methods may detect additional cancers, they also increase false positives and overdiagnosis, and their impact on mortality is unclear.

Question 37: How might genetic risk factors be incorporated into personalized screening approaches?

Incorporating genetic risk factors into screening approaches could lead to more personalized, risk-based screening strategies. Genetic factors, particularly BRCA1 and BRCA2 mutations, significantly increase breast cancer risk. Women with these mutations are often recommended to start screening earlier and may be offered more intensive surveillance, including MRI.

Beyond these high-risk mutations, researchers are exploring the use of polygenic risk scores, which consider multiple genetic variants to estimate an individual's breast cancer risk. This could potentially allow for more nuanced risk stratification, with screening frequency and modality tailored to individual risk levels. However, implementing such personalized approaches presents challenges, including the need for genetic testing infrastructure, concerns about equity of access, and the complexity of communicating personalized risk information. While promising, these approaches are still largely in the research phase and their impact on outcomes remains to be determined.

Question 38: What socioeconomic and cultural factors influence participation in mammography screening programs?

Socioeconomic factors significantly influence participation in mammography screening programs. Women with higher education and income levels are generally more likely to participate in screening. This may be due to better access to healthcare, greater health literacy, and more flexible work arrangements allowing time for screening appointments. Conversely, women from lower socioeconomic backgrounds often face barriers to screening, including lack of transportation, inability to take time off work, and concerns about costs.

Cultural factors also play a role in screening participation. In some cultures, there may be stigma or discomfort around breast examinations, particularly by male healthcare providers. Language barriers can also impact participation among immigrant populations. Religious beliefs and cultural attitudes towards preventive care can influence screening decisions. Additionally, cultural differences in risk perception and attitudes towards cancer can affect how women view the importance of screening. These socioeconomic and cultural factors contribute to disparities in screening rates and highlight the need for targeted, culturally sensitive approaches to promote equitable access to screening.

Question 39: How has media coverage affected public perceptions of mammography screening?

Media coverage has played a significant role in shaping public perceptions of mammography screening, often presenting a more positive view than is warranted by the scientific evidence. Many media reports have emphasized the benefits of screening while downplaying or omitting information about potential harms. This has contributed to widespread overestimation of the benefits of screening among the public.

Coverage of new studies or guidelines has often been sensationalized, with headlines proclaiming screening as "life-saving" or expressing alarm at any suggestion of reducing screening. When studies critical of screening have been published, they've sometimes been met with hostile media reactions, accusing researchers of endangering women's lives. This polarized coverage has made it difficult for women to access balanced information about screening. However, in recent years, some media outlets have begun to present more nuanced coverage, discussing both benefits and harms of screening, reflecting growing awareness of the complexities of the issue.

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