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In 1992, the American Cancer Society dropped its recommendation of a “baseline mammogram” at age 35, but some people still espouse the practice. For example, on a recent Internet search of “mammography at age 35,” I encountered endorsements at sites for newspaper health columns, hospitals and clinics, and women's health groups. I also encountered blogs voicing complaints by 35-year-old women that their insurance companies “didn't pay for a mammogram recommended by doctors.”
To examine the yield of mammography in young women, U.S. researchers pooled data from six mammography registries that included 120,000 women who underwent first mammograms at ages 18–39. For every 10,000 screened women in the 35–39 age subgroup (which accounted for most of the screening mammograms), 1266 underwent further work-ups, with 16 cancers detected (true-positive mammograms) and 1250 false-positive mammograms. Stated another way, 79 work-ups were conducted for each cancer detected. The detection rate was no better among women who had first-degree relatives with breast cancer. The detection rate was considerably better for symptomatic women (e.g., those with breast lumps) undergoing diagnostic mammography than for asymptomatic women undergoing screening.
Yankaskas BC et al. Performance of first mammography examination in women younger than 40 years. J Natl Cancer Inst 2010 May 19; 102:692.
Comment
The authors conclude that their findings demonstrate poor performance of mammographic screening in women aged 35–39; the cancer detection rate was 1.6 per 1000, with an extremely high false-positive rate. By comparison, the authors report (from other data) cancer detection rates of 2.3 per 1000 among women aged 40–44, and 4.3 per 1000 among women aged 45–49. Although one alleged purpose of mammography at age 35 is to serve as a “baseline,” no evidence exists that a baseline mammogram improves outcomes later on, and the mammogram becomes a screening study anyway. Moreover, whether mammography reduces breast cancer mortality in this age group is unclear. In the end, the choice of a cutoff age for mammographic screening involves value judgments; nevertheless, the arguments against screening women in their 30s are so strong that no professional organization endorses the practice for average-risk women.