A study appearing online in the Journal of the National Cancer Institute (JNCI) finds screening mammograms in women under age 40 result in high rates of callbacks and additional imaging tests but low rates of cancer detection. The study, by Bonnie C. Yankaskas, Ph.D., from the University of North Carolina at Chapel Hill, and colleagues, included 117,738 women who had their first mammogram between the ages of 18 and 39. The researchers analyzed data for both screening mammograms and diagnostic mammograms, which were performed because a woman had a warning sign or symptom, such as a lump. During one year, no cancers were detected in women under 25. Among women aged 35-39, screening mammograms had poor accuracy and high rates of recall for additional tests. The cancer detection rate in this group was 1.6 cancers per 1,000 women. For diagnostic mammograms, accuracy was better and the detection rate was 14.3 cancers per 1,000 women aged 35-39. The authors conclude that in a theoretical population of 10,000 women between ages 35 and 39 who had a screening mammogram, 1,266 would be called back for further testing, 16 cancers would be detected, and therefore 1,250 women would have false positives. An accompanying editorial says the study calls into question the recommendation of some health groups that women with a family history start screening early.We asked Otis W. Brawley, M.D., chief medical officer, to comment on the study.
“This is a very good study, and strongly supports the American Cancer Society’s advice that screening mammography should begin at age 40 and not earlier. We have been concerned that some have been encouraging that screening begin at younger and younger ages, when the science does not support it as beneficial.
“It’s important to remember that this is a study of women who have no symptoms, and are not at high risk of breast cancer due to certain genetic traits. For those women, mammography and MRI definitely do have a role in women under forty. In fact, our guidelines say that for most women at high risk, screening with MRI and mammograms should begin at age 30 and continue for as long as a woman is in good health. But because the evidence is limited regarding the best age at which to start screening, this decision should be based on shared decision making between patients and their health care providers, taking into account personal circumstances and preferences.”
For more information, including the ACS’s guidelines, see our section on “Cancer Breast Cancer Be Found Early?”