The harm and benefits of breast cancer screening
12/11/2012 § Leave a comment
Throughout 2011 and 2012, Peter Gøtzsche, director of the Norway Cochrane centre, and colleagues have created a publishing storm of articles against mammography screening for breast cancer. Their articles have appeared in the International Journal of Cancer, Lakartidningen, Radiology, Canadian Medical Association Journal, Cancer Causes & Control, BMJ, Journal of Royal Society of Medicine, and letters in the Lancet. They are clearly on a mission to convince the scientific community and through extension via the media reports that will feed off the scientific press, the public, that the harm of mammography outweighs the benefits. The titles of his various articles include: “Mammography screening: truth, lies, and controversy”; “Mortality in breast cancer is decreasing–but not because of screening. Time to abolish the mammography screening”, and “Why mammography screening has not lived up to expectations from the randomised trials.” In the latter, the abstract on the website says:
“Recent studies of tumour sizes and tumour stages show that screening has not lowered the rate of advanced cancers. In agreement with this, recent observational studies of breast cancer mortality have failed to find an effect of screening. In contrast, screening leads to serious harms in healthy women through overdiagnosis with subsequent overtreatment and false-positive mammograms. We suggest that the rationale for breast screening be urgently reassessed by policy-makers… Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.”
To address these kinds of concerns an Independent UK Panel on Breast Cancer Screening was duly formed to look at evidence from the UK programme. A summary of their assessment was printed in an early online publication by the Lancet on 30 October 2012, which is informative, coherent, and easy to understand. The Panel’s own conclusion from the evidence was:
“… that screening reduces breast cancer mortality but that some overdiagnosis occurs…for every 10, 000 UK women aged 50 years invited to screening for the next 20 years, 43 deaths from breast cancer would be prevented and 129 cases of breast cancer, invasive and non-invasive, would be overdiagnosed; that is one breast cancer death prevented for about every three overdiagnosed cases identified and treated. Of the roughly 307,000 women aged 50—52 years who are invited to begin screening every year, just over 1% would have an overdiagnosed cancer in the next 20 years…Information should be made available in a transparent and objective way to women invited to screening so that they can make informed decisions.”
In short, breast screening definitely saves lives, but it may also cause harm due to overdiagnosis. The extent of this overdiagnosis and harm in today’s world is unclear, they say, because the studies used had ‘many limitations and (their) relevance to present-day screening programmes can be questioned.’
Evidence from a focus group organised by Cancer Research UK and attended by some members of the Panel showed that many women feel that accepting the offer of breast screening is worthwhile, which agrees with the results of previous similar studies. Amen, I say. While the medical community is divided on the value of the screening programme, it is likely that women support it. If a woman has breast cancer, she would actively want to become a breast cancer patient because it is likely to be the only way to save her life. Ask me, I’ve been there, and so have the approximately 1 in 8 other women in the developed world who have had breast cancer, mostly after they pass menopause. See these articles from RHM 32 here, here, here and here.
This controversy has been raging for a long time, and in many ways has been very undermining both for health professionals and women. Hopefully the findings of the independent panel will bring some clarity and enable women to decide themselves whether to participate in the screening programme.
Gøtzsche has done us a favour in that he has exposed the possible extent of harm, which includes surgery, chemotherapy and radiotherapy that turn out after the fact not to be necessary to save a woman’s life. In a paper RHM is publishing in the November 2012 issue of the journal, the story of a woman who has had chronic pain and loss of fertility due to unnecessary treatment for cancer that did not in fact exist is described, in a qualitative study of women’s experience of three types of reproductive cancer treatment in Australia (she had suspected ovarian cancer so this isn’t actually only about breast cancer either). [Wainer et al]
The operative point here is that she learned this “after the fact”. Certainly, based on Gøtzsche’s findings, there should be a serious effort to try and figure out how to reduce overdiagnosis and overtreatment, which may indeed cause harm. He also calls for steps to reduce the incidence of cancer. Getting women not to use hormone replacement therapy had a big positive effect in that way. When we discover other proven ways to reduce the incidence of breast cancer let’s talk again. Meanwhile we must not consider throwing away the screening. Why? Because that would mean abandoning all the women whose cancers would have killed them if they went undiagnosed until too late.