Women’s views on overdiagnosis in breast cancer screening: a qualitative study
- “Women’s views on overdiagnosis in breast cancer screening: a qualitative study” by Jolyn Hersch and colleagues (BMJ 2013;346:f158, doi:10.1136/bmj.f158).
Objective—To elicit women’s responses to information about the nature and extent of overdiagnosis in mammography screening (detecting disease that would not present clinically during the woman’s lifetime) and explore how awareness of overdiagnosis might influence attitudes and intentions about screening.
Design—Qualitative study using focus groups that included a presentation explaining overdiagnosis, incorporating different published estimates of its rate (1-10%, 30%, 50%) and information on the mortality benefit of screening, with guided group discussions
Participants—Fifty women aged 40-79 years with no personal history of breast cancer and with varying levels of education and participation in screening.
Results—Previous awareness of breast cancer overdiagnosis was minimal. Women generally reacted with surprise, but most came to understand the issue. Responses to overdiagnosis and the different estimates of its magnitude were diverse. The highest estimate (50%) made some women perceive a need for more careful personal decision making about screening. In contrast, the lower and intermediate estimates (1-10% and 30%) had limited impact on attitudes and intentions, with many women remaining committed to screening. For some women, the information raised concerns, not about whether to screen but whether to treat a screen detected cancer or consider alternative approaches (such as watchful waiting). Information preferences varied: many women considered it important to take overdiagnosis into account and make informed choices about whether to have screening, but many wanted to be encouraged to be screened.
Conclusions—Women from a range of socioeconomic backgrounds could comprehend the issue of overdiagnosis in mammography screening, and they generally valued information about it. Effects on screening intentions might depend heavily on the rate of overdiagnosis. Overdiagnosis—Will be new and counterintuitive for many people and might influence screening and treatment decisions in unintended ways, underscoring the need for careful communication.
Why do the study?
Screening for breast cancer seems a simple, intuitively appealing concept. It is difficult to imagine how it could do more harm than good. The idea is to find cancers earlier, improve survival, and minimise the need for surgery. As often in medicine, however, things are not as simple as they appear.
Overdiagnosis has emerged as the most important harm of breast screening. It refers to breast cancers detected at screening that grow slowly, or not at all. Without screening, these tumours would never have been detected or caused symptoms or death in the person’s lifetime. Their detection and treatment can therefore only be harmful. It is impossible to know which individual cancers are overdiagnosed and everyone is therefore treated.
We know overdiagnosis occurs because many more cancers are detected in those offered screening than in those who are not, even when we follow up women long after screening stops. A recent independent review concluded that 4000 women are overdiagnosed every year in the United Kingdom. The review also estimated that 1300 women avoid dying from breast cancer because of screening. Both numbers are uncertain, however, and estimates in the literature vary widely.
It is important to recognise that there is no scientific answer to the question, “Should I go for breast screening?” It is a value judgment, and values differ in unpredictable ways, between individual invitees and between invitees and healthcare professionals. This study explored how various estimates of overdiagnosis influenced women’s perception of breast screening. Information in invitations does not mention overdiagnosis because those responsible for screening and information have been reluctant to acknowledge its importance and have focused on high participation rates.
As the common understanding of breast cancer is that it will inevitably progress to become lethal if not treated, overdiagnosis is counterintuitive to patients as well as to many doctors. It is therefore important to know how to explain overdiagnosis, and if women will still find breast screening worthwhile when they understand that participation substantially increases their risk of becoming a breast cancer patient.
What did the authors do?
In this qualitative study, the authors sought to understand how overdiagnosis influenced women’s views on participation in breast screening within a group of 50 women. They were of different cultural, educational, and socioeconomic backgrounds, with varying breast screening histories, and were living in Sydney, Australia. None of them had been diagnosed with breast cancer and they were in or around the age range eligible for breast screening (40-79 years).
Of 118 women initially contacted by telephone through a non-profit foundation, 78 (66%) agreed to participate in focus groups. The focus groups consisted of four to nine women, and a total of eight age stratified groups were set up. The decision to stop recruitment was based on a review of the issues raised during discussions. When no new topics came up, the researchers assumed that most issues had been addressed.
Each session lasted about two hours and included formal consent, a questionnaire at the beginning and end, a neutral presentation of the issue by a researcher, and group discussions where participants were “strongly encouraged” to ask the researcher clarifying questions . A compensation of $A150 (£102; €120; $157) was paid to each participant.
Overdiagnosis was presented as a range of estimates taken from the scientific literature: 1-10%, 30%, or 50% of breast cancers in participating women were considered overdiagnosed. This was contrasted with the mortality benefit by comparing what happens in groups of 1000 screened and unscreened women (figure 1 ).
All discussions were recorded and transcribed, and subjects raised were identified and coded by two independent researchers.
What did the study find?
Very few women had heard about overdiagnosis before this study. The concept surprised many participants who thought breast cancer was always a lethal disease if not treated, although some knew about overdiagnosis in prostate cancer screening. Most participants understood overdiagnosis at the end of the sessions. Overdiagnosis caused concern about breast screening in some women, some questioned whether overdiagnosis mattered and were concerned that it might prevent participation in others, and a few suspected a government plot to “cut out breast screening.”
Overdiagnosis particularly influenced decisions in younger women with limited screening experience, more of whom considered not participating because of it. Reactions were also dependent on the level of overdiagnosis—1-10% was not considered a substantial problem; 30% was considered problematic but not enough to give up screening; however, 50% was considered “extremely high” and made some women decide against participation, or consider a less intensive screening schedule. Some would consider a “watchful waiting” strategy rather than immediate treatment for breast cancers detected by screening if there was 50% overdiagnosis.
Many women thought that up to date information should be provided, including on overdiagnosis, allowing an informed choice. However, many also found the issue confusing, were concerned that full information would reduce participation, and would like direct encouragement to participate.
What are the strengths and limitations of this study?
The major strength of this study is that it includes a wide range of women with diverse backgrounds and most likely catches the main issues that arise when women are introduced to the concept of overdiagnosis. The thorough exploration of these issues gives a good impression of the challenges implied in providing information about the major harm of breast screening.
The weaknesses are more general to qualitative studies and have more to do with the application of the results to populations other than the comparatively small one included (the external validity), rather than the reliability of the findings for the included women (the internal validity).
Women from an urban population in Sydney might not be representative of Australia because of the selection process that prioritised many diverse backgrounds rather than obtaining a representative sample, and because those 66% who agreed to participate might have volunteered for reasons we do not know about (self selection bias). Women in other countries might also think and behave differently, even if presented with the same information.
The decision process could also differ from a real life setting because the context is different. Decisions are generally not made in a discussion group, and not with a researcher present to answer questions.
Answers and reactions will depend on how and which information was given. It can be seen as a strength that this study isolated overdiagnosis, but it can also be considered a weakness. Decisions are not based on information about overdiagnosis alone, but also false positives, false negatives, or pain at mammography, information that was not provided.
The decision process was probably substantially influenced by previous information about breast screening, previous breast screening participation, and public campaigns to make women participate. The different reactions in younger women with limited screening history support this. Arguably, this is not a weakness as such, but representative of real life.
What does this study mean?
This study confirms that women do not know about the major harm of breast screening—that participation substantially increases their risk of being diagnosed with breast cancer because of overdiagnosis. This is an important criticism of existing breast screening programmes, which have failed to acknowledge and inform women about a serious harm of the intervention for which they are responsible. Currently, most women participate without knowledge of the risks they are taking.
The study also highlights the challenges we face in explaining overdiagnosis, a concept that is new and counterintuitive. Views on breast screening will be influenced by previous campaigns to boost participation, and personal views and experiences, including whether women have participated in screening before.
The onus is on those who offer breast screening to make sure women know about and understand its benefits and harms. The focus must be changed from high uptake to high quality, balanced information that allows informed decision making and a more nuanced view of breast screening.
Baum M. Harms from breast cancer screening outweigh benefits if death caused by treatment is included. BMJ 2013;346:f385
1Nordic Cochrane Centre, Copenhagen, Denmark
Correspondence to: email@example.com
Competing interests: None declared.
Provenance and peer review: Commissioned; not externally peer reviewed.
Cite this as: Student BMJ 2013;21:f2291