Family Size Affects Breast Cancer Risk

Jun 19, 06:49 PM

Current Headlines: Women with few older female relatives carry the BRCA mutations for breast and ovarian cancer twice as often as those with larger families, say U.S. doctors.

Jeffrey Weitzel and colleagues at the City of Hope in Duarte, Calif., analyzed data on 1,543 patients seen at U.S. clinics for genetic cancer risk assessment and BRCA gene testing.

They were looking for single-case indicators, or women who developed breast cancer before age 50 but had no first- or second-degree relatives with breast or ovarian cancers. There were 306 women in the sample who met these criteria.

Half of these women had limited family structures -- less than two females who lived to age 45 on either side -- and 13.7 percent of them carried the BRCA1 or BRCA2 mutations. Only 5.2 percent of the women with larger families had inherited these genes.

Commonly used models for estimating BRCA gene mutation probability were insensitive to family structure as a predictive factor (and this) is a cautionary note for community practitioners, said Weitzel. Probability models should be reanalyzed and limited family history recorded as a separate variable.

A report on the research is published in the June 20 issue of the Journal of the American Medical Association.