A few years ago, I was visiting an old friend, a Medical School classmate, who lives in the UK. We had turned 50, and per the National Health Service guidelines, she was eligible to register for a 3 yearly screening mammogram. She had seen several friends go through this process, and be found to have DCIS (a non invasive precursor of the real culprit), and go through lumpectomy, radiation and hormonal intervention. The discussion of the reasonable management of DCIS is a topic for another day. She was reluctant to get sucked into the vortex, and was seriously considering not registering for her screenings. This led to a discussion of the real value of screening mammograms. I was reminded of that discussion as I read the update on the screening recommendations in the NEJM of June 11, 2015.
Since Breast cancer is the leading cause of female mortality from cancer in women worldwide, the goal of screening is to find it early, in asymptomatic women, so that they may undergo curative treatment, and therefore reduce mortality and morbidity from breast cancer diagnosis which will be discovered at a later time point, at a more advanced stage of disease.
In this update, screening did show a benefit in women 50 to 69 years of age who were invited to have mammographic screening. They had, on average, a 23% reduction in the risk of death from breast cancer; women who attended mammographic screening had a higher reduction in risk, estimated at about 40%.
So why not screen?
The most important harms associated with early detection of breast cancer through mammographic screening are false positive results, over diagnosis, and possibly radiation-induced cancer. This was the reason that my friend did not want to participate. Unfortunately the adjunct use of ultrasounds, CT scans or MRIs increase, rather than decrease the risk of false positives. Ultrasound does increase the diagnosis of breast cancer in women with dense breasts, but also increases false positives, and CT scans increases radiation exposure, without benefit.
While Radiation-induced breast cancer is a concern in women who are offered screening, the estimated risk is smaller by a factor of at least 100 than the risk of death from breast cancer.
In 2002, on the basis of findings from randomized, controlled trials, the previous IARC Handbook Working Group concluded that the evidence for the “efficacy of screening by mammography as the sole means of screening in reducing mortality from breast cancer” was sufficient for women 50 to 69 years of age, limited for women 40 to 49 years of age, and inadequate for women younger than 40 or older than 69 years of age.
In 2015, an update has been published in the NEJM.
Breast-Cancer Screening — Viewpoint of the IARC Working Group
Béatrice Lauby-Secretan, Ph.D., Chiara Scoccianti, Ph.D., Dana Loomis, Ph.D., Lamia Benbrahim-Tallaa, Ph.D., Véronique Bouvard, Ph.D., Franca Bianchini, Ph.D., and Kurt Straif, M.P.H., M.D., Ph.D. for the International Agency for Research on Cancer Handbook Working Group
N Engl J Med 2015; 372:2353-2358June 11, 2015DOI: 10.1056/NEJMsr1504363
The working group still concludes that there is a net benefit from inviting women 50 to 69 years of age to receive screening. A substantial reduction in the risk of death from breast cancer was also consistently observed in women 70 to 74 years of age who were invited to or who attended mammographic screening. The risk reduction due to screening in women 40 to 44 or 45 to 49 years was generally less pronounced. Overall, the available data did not allow for establishment of the most appropriate screening interval.
What is the benefit of self examinations?
A lot of women are reluctant to do those for several reasons. One reason is that they “don’t know what they are looking for.” Another, even in Breast Cancer Survivors, they are afraid of what they may find.
Clinical breast examination is a simple, inexpensive technique. In three trials in which women were randomly assigned to receive either clinical breast examination or no screening, breast cancers detected at baseline and in the early years of the trials tended to be of a smaller size and less advanced in the self examination group. In addition, five observational studies, conducted mostly in the 1970s, reported that clinical breast examination combined with mammographic screening increased the breast-cancer detection rate by 5 to 10 percentage points as compared with mammography alone. While the available data did not show a reduction in breast-cancer mortality when breast self-examination was either taught or practiced competently and regularly, it may be that the numbers of women who report practicing breast self-examination are probably too few to have had an effect on mortality from breast cancer.
My advice to my patients is to continue with breast self examinations every month. You see your physician only every 4-6 months, and get a mammogram every 12 months. Your self examination is your first line of defense.
What should we do for High Risk Patients? Those with a strong family history or genetic predispositions?
The use of MRI as an adjunct to mammography significantly increases the sensitivity of screening in women with a high familial risk and a BRCA1 or BRCA2 mutation as compared with mammography alone. The data are not so strong for other high risk groups, and MRIs do carry the risk of false positives, and have been associated with an increasing choice of mastectomy over lumpectomy. The sensitivity of ultrasonography was found to be similar to or lower than that of mammography and was consistently lower than that of MRI.
At the end of that discussion with my friend a few years ago, she did change her mind, and registered for the screening program. The benefit for mortality and morbidity reduction of invasive breast cancer is clear.