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BRCA Risk Variants May Coincide With Breast Cancer Treatment Differences

NEW YORK – Results from a new analysis suggest women carrying risky BRCA1 or BRCA2 mutations who are diagnosed with breast cancer may be less apt to receive cancer treatment dictated by current practice guidelines than BRCA mutation-free breast cancer patients.

"We need to understand this gap better, because it could have potential implications on patients' outcomes," senior author Steven Katz, a general medicine, and health management and policy researcher affiliated with the University of Michigan and Stanford University, said in a statement.

For a paper published in JAMA Oncology on Thursday, Katz and his colleagues looked at treatment histories for 20,568 stage 0 to stage III breast cancer patients using information from "Surveillance, Epidemiology, and End Results" (SEER) registries in Georgia and California. They found that the proportion of patients who received surgical intervention, radiation, or chemotherapy between 2014 and 2016 all varied to some extent depending on the patients' BRCA mutation status.

When it came to radiation treatment, for example, the team found that 82 percent of BRCA1/2 mutation-free breast cancer patients got radiation when they were candidates for it, relative to just over half the BRCA mutation-positive breast cancer patients.

And more than two-thirds of the breast cancer patients with inherited risk variants had had double mastectomy surgeries, versus fewer than one-quarter of the breast cancer patients with a negative panel test.

On the other hand, the SEER data indicated that women with risky germline variants in BRCA1 or BRCA2 were more likely, on average, to receive chemotherapy when guidelines said they could omit it based on a 21-gene recurrence score, cancer stage, and tumor features. The researchers noted that some 30 percent of inherited mutation-free patients still got chemo when they could potentially skip it based on a broader favorable prognosis, compared to 38 percent of patients in the BRCA mutation-positive group.

When the team expanded its analysis to include women with pathogenic variants in other breast cancer-related genes such as CHEK2, PALB2, or TP53, it saw similar treatment disparities for breast cancer patients with or without the risk variants.

"We found that breast cancer treatment among women who test positive for an inherited genetic mutation is less in line with practice guidelines, in particular for radiation therapy and chemotherapy," first author Allison Kurian, a medicine, health research and policy researcher at Stanford, said in a statement, noting that it is "challenging to integrate genetic testing into breast cancer care."

Although testing with germline genetic testing panels for inherited cancer-related variants is on the rise, the team explained, it is not entirely clear how the results of such tests might impact care, if at all, for breast cancer patients who do carry cancer susceptibility variants.

Based on the current analysis of early-stage breast cancer patients in two states, the authors suggested that the treatment received by women with risky variants in BRCA1, BRCA2, or other breast cancer-related genes "may be less concordant with practice guidelines, particularly for radiotherapy and chemotherapy."