What exactly is “overdiagnosis” of breast cancer?
Overdiagnosis is the diagnosis of a tumor that would not have become clinically apparent in the absence of screening. Treatment of an overdiagnosed tumor cannot provide benefit, but it can lead to harm. Overdiagnosis and overtreatment are now widely acknowledged to be an important harm of medical practice, including cancer screening.[1] In the case of breast cancer, for example, DCIS was rarely diagnosed before screening was adopted.[2] Yet tens of thousands of women in North America diagnosed with DCIS will have aggressive locoregional treatment, often a lumpectomy or mastectomy followed by radiotherapy and sometimes hormonal therapy as well.
There is as yet no sure estimate regarding the extent of overdiagnosis and overtreatment with estimates in the literature cover a frustratingly broad range.[3] There is, however, broad agreement that DCIS is particularly susceptible to overdiagnosis.
The new paradigm of the complexity of cancers
It is now understood that breast cancer is not one disease, but a range of diseases requiring different treatments. Furthermore, tumors do not progress at a steady rate. Indolent tumors may stop growing, grow very slowly or even regress. All this is leading to a new paradigm of complexity regarding cancer and cancer treatment.
Population-wide screening programs are based on the assumption that cancer has an orderly and gradual progression which will eventually become lethal if left untreated. But the simplistic dictum that early breast cancer detection saves lives is increasingly problematic as it causes harm to those women whose tumors would have remained harmless but are nonetheless subjected to unnecessary surgery, radiation, possibly chemotherapy and hormonal therapy. These women are then labeled for the rest of their lives as having had breast cancer with all the medical, financial and social consequences that this creates.
In 2012, the U.S. National Cancer Institute organized a “brainstorming meeting” of a panel of cancer specialist and patient advocates to address the issue of cancer overdiagnosis. The Panel issued the following consensus regarding overdiagnosis and overtreatment:[4] It proposes that we must recognize that overdiagnosis occurs and is common and develop new terminology to replace the word “cancer” for the classification of low-risk lesions. It also suggests the creation of observational registries for low-risk lesions and the adaption of our detection methods to avoid identifying unimportant lesions. Finally, they suggest that we need new strategies on how to approach breast cancer progression and prevention.
We at Breast Cancer Action Quebec understand deeply just how scary the words “breast cancer” are for any woman. But too many women are being unnecessarily treated for lesions that would never have caused problems.
For women to better understand the issue of overtreatment, we need to change discussions of breast cancer from fear-mongering approaches of “one in nine” to an understanding that it is a complicated set of diseases requiring very different approaches, and in some cases, no intervention, but rather an attentive surveillance. We need a discussion on current screening programs, a reexamination of the treatment of DCIS and the development of less aggressive treatments, as well as the creation observational registries to study the evolution of these cases. We also clearly need better coordination of breast cancer research agendas so that fundamental research on tumor biology is made a priority.
Individual women must be informed, prepared and encouraged to enter into these discussions with their doctors when the diagnosis of breast cancer is first raised. And finally, women in the women’s health movement must be included in these discussions to develop the tools necessary to bring about these changes.
[1]Elmore, Joann G. and Ruth Etzioni (2015). Effect of Screening Mammography on Cancer Incidence and Mortality. Invited Commentary. JAMA Internal Medecine. Published online July 6, 2015. Downloaded from http://archinte.jamanetwork.com/on 07/072015.
[2]Esserman, Laura, J. and colleagues (2014). Addressing overdiagnosis and overtreatment in cancer : a prescription for change. Lancet Oncology. May 2014. 15(6) : e234-242.
[3]Elmore and Etzioni, op. cit.
[4]Esserman and colleagues. op.cit.
This leaflet, developed by the independent research centre, The Cochrane Collaboration, provides necessary, basic information about the benefits and harms of screening. As the information women receive when they are invited to attend for screening with mammography is often insufficient, one-sided or erroneous, this leaflet enables women to make a free and informed decision whether to attend for screening.
