Characterization of male breast cancer: Results of the EORTC 10085/TBCRC/BIG/NABCG International Male Breast Cancer Program

Abstract

Background

Male breast cancer (BC) is rare, managed by extrapolation from female BC. The International Male BC Program aims to better characterize and manage this disease. We report the results of part 1, a retrospective-joint-analysis of cases diagnosed during a 20-year-period.

Methods

Patients with follow-up and tumor samples, treated between 1990-2010, in 93 centers/nine countries. Samples were centrally analyzed in three labs (UK, NL, US).

Results

Of 1822 patients enrolled, 1483 were analyzed; 63.5% were diagnosed between 2001-2010, 57 (5.1%) had metastatic disease (M1). Median age at diagnosis: 68.4 years. Of 1054 M0 cases, 56.2% were node-negative (N0) and 48.5% had T1 tumors; 4% had breast conserving surgery (BCS), 18% sentinel lymph-node biopsy; half received adjuvant radiotherapy; 29.8% (neo)adjuvant chemotherapy and 76.8% adjuvant endocrine therapy (ET), mostly tamoxifen (88.4%). Per central pathology, for M0 tumors: 84.8% ductal invasive carcinomas, 51.5% grade 2; 99.3% ER-positive; 81.9% PR-positive; 96.9% AR-positive (ER, PgR or AR Allred score ≥3); 61.1% Ki67 expression low (<14% positive cells); using IHC surrogates, 41.9% were Luminal-A-like, 48.6% Luminal-B-like/HER-2-negative, 8.7% HER-2-positive, 0.3% triple negative. Median follow-up: 8.2 years (0·0-23·8) for all, 7.2 years (0·0 -23·2), for M0, 2.6 years (0·0-12·7) for M1 patients. A significant improvement over time was observed in age-corrected-breast-cancer-mortality. Breast-cancer-specific-mortality was higher for men <50 years. Better OS and RFS were observed for highly-ER + (p = 0·001), highly-PR + (p = 0·002), highly-AR+ disease (p = 0·019). There was no association between OS/RFS and HER-2 status, Ki67, IHC subtypes nor grade.

Conclusions

Male BC is usually ER, PR, and AR positive, Luminal B-like/HER2-negative. 56% patients had T1 tumors but only 4% had BCS. ER was highly positive in > 90% of cases but only 77% received adjuvant ET. ER, PR, and AR were associated with OS and RFS, while grade, Ki67, and IHC surrogates were not. Significant improvement in survival over time was observed.