Studies examine risk-based mammography screenings

According to two new studies published in the May 1 issue of Annals of Internal Medicine, younger women at increased risk for breast cancer may benefit from biennial mammography screening beginning at age 40.

Currently, major organizations with mammography screening guidelines do not have a consensus on whether to routinely screen all women in their 40s. These data have implications for risk-based screening programs.

In the first study, researchers evaluated data from 66 published articles and from the Breast Cancer Surveillance Consortium to determine the factors associated with an increased risk for breast cancer in women aged 40 to 49. Of the 13 possible risk factors examined, the data showed that having extremely dense breast tissue and a first-degree relative with breast cancer (parent, sibling, or child) doubled a woman’s breast cancer risk. The risk was even higher for a woman with more than one first-degree relative with breast cancer or first-degree relatives with a diagnosis before age 50. Having a prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts increased a woman’s risk by 1.5- to 2-fold; and current use of oral contraceptives, never giving birth to a child, or giving birth to a first child after age 30 increased a woman’s risk by 1.0- to 1.5-fold.

Quantifying risk associated with known risk factors may be useful to women and their doctors as they decide when to start mammography screening, the study authors reported.

In the second study, researchers used four independent models to examine what level of risk tips the balance of benefits and harms to favor screening mammography for women aged 40 to 49. The researchers compared mammography screening starting at age 40 versus age 50 using either digital or film mammography. The researchers also compared annual and biennial screening intervals to determine which approach yielded the most benefits (life-years gained, breast cancer deaths averted) and least harms (false-positives). The researchers found that for women aged 40 to 49 with a two-fold increased risk for breast cancer, the harm-benefit ratio of biennial screening with film mammography was similar to that of biennial screening of average-risk women aged 50 to 74. 

“The evidence suggests that for women at twice the average risk for breast cancer, biennial screening beginning at age 40 has more benefits than harms,” said study lead author Nicolien T. van Ravesteyn, MSc, of the Department of Public Health, Erasmus MC, Rotterdam, The Netherlands. “These results provide important information toward developing more individualized, risk-based screening guidelines.”

According to Otis Brawley, MD, chief medical and scientific officer, executive vice president of the American Cancer Society and author of an accompanying editorial, the public needs to be educated about the benefits and risks of mammography so that individual risk factors and patient preferences (based on knowledge of benefits and harms) can be considered when making screening decisions. Brawley writes that the public perceives mammography as a better technology than it actually is. It is important to carefully weigh the harm-benefit ratio for a specific woman before advising use of the test.

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