The 21-Gene Recurrence Score in Male Breast Cancer

Given the limited data, systemic treatment of male breast cancer has been extrapolated from female patients. The 21-gene recurrence score (RS) assay estimates the risk of distant recurrence and chemotherapy benefit in early-stage, ER+/HER2- female breast cancer. We assessed the association between RS and type of treatment in male breast cancer.

We identified male patients with ER+/HER2- breast cancer and available RS results treated at our institution in 2006-2016. We collected data on clinicopathologic features, treatment, and outcome. The Institutional Review Board approved the study.

The study cohort consists of 38 male breast cancer patients with a median age of 70 years. Median tumor size was 1.6 cm, and 81.6% (31) were node-negative. RS was low (≤ 17) in 26 (68.4%) cases, intermediate (18-30) in 9 (23.7%) cases, and high (≥ 31) in 3 (7.9%) cases, comparable to that in female patients at our institution. All patients underwent total mastectomy, and one received radiotherapy. Thirty-four (89.5%) patients received adjuvant endocrine therapy, mostly tamoxifen (81.6%; 31). Five (13.2%) patients with intermediate or high RS were treated with adjuvant chemotherapy. No locoregional recurrence was observed, and one patient developed distant recurrence (median follow-up 34 months).

The RS distribution in male breast cancers was similar to that in females treated at our institution. With limited follow-up, patients with low RS were spared chemotherapy and did not develop recurrence. Our results suggest that the RS may have a clinical utility in male breast cancer patients.