Bilateral mastectomy and breast-conserving surgery have equal impact on breast cancer-specific mortality in pathogenic BRCA1 carriers

Women with breast cancer with a pathogenic BRCA1 variant who undergo bilateral mastectomy are significantly less likely to develop contralateral breast cancer. However, bilateral mastectomy is not significantly associated with a reduction in long-term breast cancer-specific mortality compared with breast-conserving surgery, as is shown by interim results from an international study.

Pathogenic variants in BRCA1 and BRCA2, which are found in 3–4% of women with breast cancer, increase the risk of ipsilateral and contralateral breast cancer, as well as the risk of ovarian cancer. For this reason, many women with a BRCA-mutated unilateral breast cancer opt for bilateral mastectomy. However, it is not clear to what extent this operation impacts long-term breast cancer mortality. An international study, initiated at the University of Toronto, thus evaluated the differences in survival by surgical treatment in an international cohort of women with a BRCA1 mutation and unilateral breast cancer. Dr Kelly Metcalfe (Women’s College Research Institute Toronto, Canada) presented the interim results [1].

A total of 2,482 patients with stage I–III, BRCA1-mutated, unilateral breast cancer (mean age 43 years) were enrolled; 34.3% underwent breast-conserving surgery, 46% underwent unilateral mastectomy, and 19.7% underwent bilateral mastectomy.

Among those who had a unilateral mastectomy or breast-conserving surgery, the risk of contralateral breast cancer at 20 years was 27.5%. After experiencing a contralateral cancer, the hazard ratio for breast cancer-related death was 2.22 (95% CI 1.49–3.32; P<0.0001) compared with patients without contralateral breast cancer, regardless of age. Of all patients, 11.5% died of breast cancer during follow-up. The 15-year breast cancer-specific survival in the entire cohort was 82.9%. The survival was 78.7% for those who had a unilateral mastectomy, 86.2% for those who had breast-conserving surgery, and 88.7% for those who had bilateral mastectomies. Age was not correlated to survival.

“What we see from these data is that women with breast cancer with a pathogenic BRCA1 variant who have bilateral mastectomy are significantly less likely to develop contralateral breast cancer. However, bilateral mastectomy is not significantly associated with a reduction in mortality compared with breast-conserving surgery,” concluded Dr Metcalfe. “The cohort will require longer follow-up for definitive results, and additional analyses are ongoing.”

1. Metcalfe KA, et al. Surgical treatment of women with breast cancer and a BRCA1 pathologic variant: an international analysis of the impact of bilateral mastectomy on survival. GS02-04, SABCS 2023, 5–9 December, San Antonio, TX, USA.

 

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Posted on 11 January, 2024