Clinical, biological characteristics of male breast cancer
Men with breast cancer have tumours that are typically of the human epidermal growth factor receptor 2 (Her2)-negative Luminal B subtype and positive for oestrogen receptor (ER), progesterone receptor (PR) and androgen receptor (AR), according to the results of the EORTC 10085/TBCRC/BIG/NABCG International Male Breast Cancer Program study.
The study included 1,483 male breast cancer patients (median age at diagnosis 68.4 years) treated between 1990 and 2010 at different centres in nine countries.
In the group of 1,054 patients with nonmetastatic disease, 56.2 percent were node-negative (N0), 48.5 percent had T1 tumours, 4 percent underwent breast conserving surgery, 18 percent had sentinel lymph-node biopsy, 50 percent received adjuvant radiotherapy. There were 29.8 percent who received (neo)adjuvant chemotherapy and 76.8 percent who were on adjuvant endocrine therapy, mostly tamoxifen (88.4 percent).
Central pathology assessment of nonmetastatic tumors revealed that 84.8 percent were ductal invasive carcinomas and 51.5 percent were grade 2. Tumours were ER-positive in 99.3 percent, PR-positive in 81.9 percent and AR-positive in 96.9 percent (ER, PR or AR Allred score ≥3). A total of 61.1 percent had low Ki67 expression (<14 percent positive cells). Using IHC surrogates, 41.9 percent were Luminal-A-like, 48.6 percent were Luminal-B-like/HER-2-negative, 8.7 percent were HER-2-positive, and 0.3 percent were triple negative.
Median follow-up was 8.2 years overall, 7.2 years in the group of patients with nonmetastatic disease and 2.6 years in the group with metastatic disease. There was a significant improvement seen over time in age-corrected breast cancer mortality. Breast cancer-specific mortality was higher for males aged <50 years. Superior overall and relapse-free survival were observed in patients with highly ER-positive (p=0.001), highly PR-positive (p=0.002) and highly AR-positive disease (p=0.019).
Overall and relapse-free survival showed no association with HER-2 status, Ki67, IHC subtypes or tumour grade.