Breast cancer is the most common cancer diagnosed in women younger than 40 in the U.S. Women who are diagnosed at a young age (under 50) are encouraged to undergo genetic testing to determine if they are carriers of BRCA1 and BRCA2 genetic mutations, since assessing this can have implications for subsequent treatment decisions.

A new article reports genetic testing for BRCA mutations has increased among women diagnosed at a young age. Dr. Ann H. Patridge, of the Dana-Farber Institute in Boston, and co-authors set out to examine the rate of women who actually underwent the recommended testing, and how concerns about genetic information affected treatment decisions. The study included 897 women aged 40 and younger who were diagnosed with breast cancer throughout 11 different medical centers.

The findings, reported in JAMA Oncology, showed 87 percent of women underwent BRCA testing within a year after breast cancer diagnosis, and the frequency of testing increased over time. Of women diagnosed in 2006, 76.9 percent report undergoing testing, and the proportion of women tested increased in following years — 96.6 percent were tested in 2012 and 95.3 percent were tested in 2013, according to the results.

Of the women who were tested, 7.6 percent had a BRCA1 mutation, and 4.5 percent reported a BRCA2 mutation (4.6 percent reported an unknown or indeterminate result). The data also showed these results had a significant impact on women’s decisions regarding treatment, with 29.8 percent of women who received a positive or negative result saying this knowledge influenced their treatment in some way. About 86 percent of mutations carriers opted for a bilateral mastectomy, and carriers of a mutation were also more likely than noncarriers to undergo a salpingo oophorectomy (ovary removal). Interestingly, there was a relatively high rate of bilateral mastectomy among noncarrier women (51.2 percent) as well.

The authors say the high frequency of BRCA testing is likely due to the fact that most of the study participants were insured, educated, and treated at medical centers where testing and treatment services were widely available. They also suggest widespread media attention to genetic breast cancer risks ( known as the "Angelina Jolie effect") could have influenced women enough that they bring up the issue with their doctor.

The authors concluded: “Given that knowledge and concern about genetic risk influence surgical decisions and may affect systematic therapy trial eligibility, all young women with breast cancer should be counseled and offered genetic testing, consistent with the National Comprehensive Cancer Network Guidelines.”

Source: Rosenberg S, Ruddy K, Tamimi R, Gelber S, Schapira, Come S, et al. BRCA1 and BRCA2 Mutation Testing in Young Women With Breast Cancer. JAMA Oncology. 2016.