(ChemotherapyAdvisor) – Younger women at increased risk for breast cancer may benefit from biennial mammography screening beginning at the age of 40, according to two studies published in the May 1 issue of Annals of Internal Medicine.

“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.”

The first study evaluated data from 66 published articles and from the Breast Cancer Surveillance Consortium to determine factors associated with an increased risk for breast cancer in women aged 40 to 49 years. Of 13 possible risk factors, the investigators found that having extremely dense breast tissue and a first-degree relative with breast cancer (parent, sibling, or child) doubled a woman’s risk of breast cancer. 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 the age of 50 years.

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Risk was increased by 1.5- to 2-fold if a woman had a prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts and by 1.0- to 1.5-fold with current use of oral contraceptives, never giving birth to a child, or giving birth to a first child after age 30 years.

The second study 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 years.

Mammography screening results starting at age 40 vs. 50 years using either digital or film mammography were compared, as were 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 years with a 2-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 years.

“Reducing the false-positive rate is crucial to improving the balance of benefits and harms for screening regimens for women of all ages,” investigators for the second study wrote. In addition, quantifying risk associated with known risk factors may be useful to women and their clinicians as they decide when to initiate mammography screening.


Abstract for Meta-analysis