This new guideline has been widely reported in the news and has received a plethora of media attention. I’ve also been asked by patients how this will impact my advice… so I thought I would devote this week’s article to the subject of breast cancer screening.
First, just the facts: Breast cancer is the most common cancer in women. In the United States an estimated 231,840 women will be diagnosed with breast cancer in 2015. Second only to lung cancer, it is the leading cause of cancer deaths in women and it is the primary cause of premature mortality for women. And according to the recent article in JAMA, in 2012, deaths from breast cancer accounted for 783,000 years of potential life lost and an average of 19 years of life lost per death. There has, however, been a steady decline in breast cancer mortality and this is largely due to improvements in early detection and treatment. Yet an estimated 40,290 women in the United States will die of breast cancer in 2015; so obviously we have a long way to go…
The American Cancer Society’s new recommendation for screening was updated from that which they issued in 2003. Their committee considered estimated harms associated with screening (false positives and unnecessary additional tests, biopsies and anxiety) and mortality benefits. They tried to find a balance between desirable and undesirable outcomes, the diversity in women’s and physicians values and preferences and then define their recommendations as either “strong” or “qualified”. They defined “strong” choices by stating that most individuals in the situation would want the recommended course of action. “Qualified” was meant to indicate that the majority of individuals would want the suggested course of action but many would not. They also defined “average risk” women as those with no personal history of breast cancer, no confirmed or suspected genetic mutation known to increase risk and no history of previous radiotherapy to the chest at a young age. They also stated that there are women outside of these risk categories who are still at a higher-than-average, risk of breast cancer, and for whom mammography alone may be less effective. These included women with significant family history who do not have a high probability of being carriers of identified mutations, women with the prior diagnosis of benign proliferative breast disease (usually diagnosed with multiple biopsies in the past), and women with significant mammographic breast density. (And here I want to state that up to 10% of women have extreme density in their mammogram and 40% have what’s called heterogeneous density, which means moderately dense.)
So, if you don’t fall into a high risk category (or higher risk) this is what the ACS recommends:
Women with an average risk of breast cancer should undergo regular screening mammography starting at age 45 (strong recommendation).
Women age 45 to 54 years should be screened annually (qualified recommendation).
Women 55 years and older should transition to biannual screening or have the opportunity to continue screening annually (qualified recommendation).
Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation).
The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation).
A few personal comments… the reason the ACS suggested starting at 45 instead of 40 in low risk women was that the five-year absolute risk of breast cancer between 40 and 44 is “only” 0.6% but at 45 to 49 it increases to 0.9%. The younger a woman, the denser her breasts which makes mammogram more difficult to read. This means that there is a greater chance of finding “something” that then mandates further testing and even biopsy (a false positive). The committee felt that the chance of this occurring was too high and the chance of cancer too low in a younger population of women to warrant screening mammograms. But they also realized that women might want earlier screening because it had been recommended (by them) in the past and/or they have significant breast cancer fears. Moreover, many clinicians might want to “play it safe” and recommend mammogram screening in women between 40 and 45. In that case, the ACS emphasizes that their current recommendation be followed with a discussion of the pros and cons of screening mammograms at an earlier age.
When breast cancer develops in relatively young premenopausal women between the ages of 45 and 54, it tends to be more aggressive and grow faster than when it develops in older women. Therefore the ACS has recommended yearly mammogram in this age group. Studies have shown that yearly screening in this age group can detect cancer at an earlier stage and help reduce mortality. Breast cancer in postmenopausal women who are not on hormone therapy tends to grow more slowly and the mortality from this “later” cancer does not seem to be impacted by reducing screening intervals to every two years. Once more, however, the ACS does not want to prevent annual screening for post menopausal women and they state that “women 55 years and older should also have the opportunity to continue screening annually.”
Breast cancer incidence continues to increase with age and 26% of breast cancer deaths each year are attributable to a diagnosis after age 74. However, the reduced life expectancy associated with being older decreases the likelihood of a screening benefit for some women who are in poor health. The good news is that a significant portion of women 75 years and older are in good health and can be expected to live considerably longer than 10 more years. According to the 2010 US life tables, 50% of 80-year-old women and 25% of 85-year-old women will live at least 10 years longer. So the ACS concludes that for women who are healthy and have at least a 10 year longer life expectancy, individualized decisions about screening mammogram should be considered.
Now I want to address the recommendation against clinical breast examination (CBE) for breast cancer screening. The ACS felt that there was moderate evidence that adding CBE to mammography screening increased the false positive rate. They also point out, however, that there are some studies that have shown that CBE will detect a small number of additional breast cancers (2% to 6%) compared with mammography alone. They found no data on whether patient outcomes are improved with CBE. Given that there was insufficient data about significant benefit and there was data on an increase in false positive rates, they decided not to recommend CBE. They also stated that there are time constraints in a typical clinic visit and that clinicians should use this time instead for ascertaining family history and counseling women to be alert to breast changes and the potential benefits, limitations and harms of screening mammography. Personally, I found this latter consideration to be inappropriate. There’s no reason why a clinician cannot talk to a patient while she or he is examining their breasts. The American Congress of Obstetricians and Gynecologists continue to recommend clinical breast exams. I have in the past found cancers in women who have had “normal” mammograms. I know this is anecdotal but it was very meaningful to these women and I will continue to perform CBE when my patients come to see me.
The ACS recommendations are not written in stone and they differ from other organizations which makes this confusing. I hope I was able to explain what they did suggest. In their final conclusions the ACS recognizes “that the balance of benefits and harms will be close in some instances and that the spectrum of women’s values and preferences will lead to varying decisions. The intention of this new guideline is to provide both guidance and flexibility for women about when to start and stop screening mammography and how frequently to be screened for breast cancer”.
Once more I will end this fairly long website article with the usual “Discuss this with your physician…”