Controversy has surrounded the utility of screening mammograms, particularly in women in their 40s. In 2009, the US Preventive Services Task Force recommended that screening mammography begin at age 50 and that women aged 50 to 74 receive a mammogram every 2 years.1 However, the American Cancer Society2 and other professional groups continue to recommend that annual screening begin at age 40, leading to controversy and confusion among women’s health clinicians and our patients.
In a recent study, Webb and colleagues3 used registry data based on a health plan in a single US city to assess the cause of death and mammogram history of 1,705 women who died following a diagnosis of invasive breast cancer from 1990 to 1999. They confirmed that 609 of these deaths were from breast cancer. How many of these patients were screened?
What did they find? The investigators found that 29% of the 609 women who died from breast cancer had been screened for it—19% of the cancers that caused death were screen-detected and 10% were interval cancers. (Interval cancers were defined as symptomatic or palpable tumors that presented less than 2 years after the prior screening mammogram.) That means that 71% of 609 deaths from breast cancer were among unscreened women, with 6% of the fatal cancers diagnosed more than 2 years after the last mammogram and 65% never found upon screening because screening did not occur.
Among deaths caused (n = 609) and not caused (n = 905) by breast cancer, the median age at diagnosis was 49 and 72 years, respectively. Investigators concluded that regular screening of women younger than age 50 years would lower the death rate from breast cancer.
Let’s not jump to any conclusions Although some may find the report by Webb and colleagues persuasive, I am concerned about this study’s limitations, of which there are a few. First, analyses that focus on women diagnosed with breast cancers do not allow comparison of outcomes among screened and unscreened populations.
Moreover, this report provides no information on treatment received by screened and unscreened women. It is likely that women who have never been screened, or who have been screened only infrequently, are considerably less affluent and less educated than women who are regularly screened. Accordingly, upon noting a palpable breast mass, unscreened women may be less likely to seek timely medical attention than regularly screened women, leading to differences in breast cancer outcomes, which are independent of screening history.
How I counsel my patients For now, I will continue to be laissez-fare in my recommendations about screening mammograms for average-risk women in their 40s by supporting their individual preferences about when to initiate such screening.