Experts continue to disagree on timing and other aspects of breast cancer screening. Guidelines for when to start and how often to screen vary, with the U.S. Preventive Services Task Force recommending biennial screening mammography for women ages 50 to 74 while the American Cancer Society recommends women ages 45 to 54 undergo annual screening and women ages 55 and older undergo biennial screening.

Arguments against breast cancer screening are based on harm reduction principles. One argument posits that many of the cancerous lesions (25% to 30%), usually ductal carcinoma in situ, that mammograms detect would never advance to invasive malignancy and thus women are unnecessarily subjected to difficult and life-changing treatments, including surgery, radiation, and hormonal therapy. Another argument is that mammograms have a high rate of false-positive results. According to a study by Ho and colleagues in the March JAMA NetworkOpen, half of all women who get annual screenings will have a false-positive result in 10 years of screening. False positives lead to unnecessary diagnostic workups that may include breast biopsies. False positives can also cause significant anxiety in women who experience them; some report living with fear and uncertainty while waiting for a definitive diagnosis.

Now there is evidence that overdiagnosis in mammography is not as prevalent as once thought. In a new study in the April issue of Annals of Internal Medicine, Ryser and colleagues analyzed the results of screening mammograms for over 35,000 women and found that only 15% of screen-detected cancers resulted in overdiagnosis; 6% were indolent preclinical cancers and 9% were progressive preclinical cancers in women who would have died from other causes before clinical diagnosis.

The timing of mammography screening-and even the decision about whether to have mammography at all-is an individual one, made in consultation with a woman's primary care provider. This study suggests that for individual women choosing to undergo screening is unlikely to lead to overdiagnosis and the toll it can take.-Karen Roush, PhD, RN, FNP-BC, news director