SAN ANTONIO – No difference in outcomes was seen among young BRCA gene mutation carriers and noncarriers with early-stage invasive breast cancer in a large cohort in the United Kingdom, but a subgroup analysis of those with triple-negative breast cancer showed a clear survival advantage among BRCA mutation carriers.
The findings of the POSH (Prospective Study of Outcomes in Sporadic Versus Hereditary Breast Cancer) trial have important implications for treatment decision making – particularly with respect to surgery – for younger women with breast cancer, according to Diana M. Eccles, MD, of the University of Southampton (England) and University Hospital Southampton Foundation Trust.
The overall finding of no difference in outcomes – including for the primary endpoint of overall survival and secondary endpoints of overall and distant disease-free survival – was true in both univariate and multivariable analysis of data for 2,759 women (14% with BRCA mutations), aged 40 years and younger, who were enrolled over an 8-year period, beginning in 2000, from 126 oncology centers across the United Kingdom, and who were followed for a median of 8.2 years, Dr. Eccles reported at the San Antonio Breast Cancer Symposium.
“We looked at BRCA1 and BRCA2 separately, and we still could see absolutely no difference in survival between BRCA1 and BRCA2, and we were well powered to show a difference,” she said, noting that 99% of these patients were diagnosed based on symptomatic presentation and did not know they were BRCA mutation carriers.
The findings were different among 511 patients with triple-negative breast cancer, however,
“Here we did see a clear difference in survival in favor of BRCA gene carriers – 11% at 10 years. And what was interesting was this clear time-varying hazard of relapse, with the maximum benefit of surviving in the BRCA gene carriers observed in the first few years with a hazard for relapse at 5 years equivalent between the two groups,” she said.
The primary treatment approach in these patients was no different than that in the group as a whole, Dr. Eccles noted, explaining that those with and without triple-negative disease had similar usage of breast conserving vs. unilateral surgery and similar usage of anthracycline-based chemotherapy regimens, with taxane added in a small proportion, which was “very typical for treatment regimens at the time.”
A proportion of women with BRCA gene mutations that were found in the clinical setting had opted to have bilateral mastectomy (15% vs. 3% of noncarriers) “closely following or during their primary treatment diagnosis,” and a separate analysis showed an intriguing survival benefit among those who did not have bilateral mastectomy; survival was 2% better among those women at 5 and 10 years, again with a time-varying hazard, Dr. Eccles said, noting, however, that the study was not powered to show a difference in this measure.
“It’s intriguing that bilateral mastectomy after diagnosis does not seem to improve survival in these young gene carriers. These are very small numbers so we have to be careful, but this is good news for patients. Many patients believe that being a BRCA gene carrier, or even just having a family history is going to give them an adverse prognosis, and that’s clearly not true – and it’s also important that patients who are facing the difficult, difficult decisions around chemotherapy and breast cancer treatment don’t feel compelled to make a decision about bilateral mastectomy within that time shortly after their diagnosis and can reasonably reserve judgment about the extent of surgery until a later date,” she said.
She discussed her findings further in a video interview.