Abstract P6-19-02: Tumor subtypes and survival in male breast cancer: SEER 2010-2014

Abstract

Abstract Background: Male breast cancer (MaBC) is an uncommon disease, and population-based information regarding prognostic factors is limited. Most MaBC are hormone receptor (HR) positive, however, the association of tumor subtypes with overall survival (OS) and breast cancer-specific survival (BCSS) is unclear. The aim of this study was to analyze the characteristics of each tumor subtype and its impact on OS and BCSS. Methods: Using Surveillance, Epidemiology, and End Results (SEER) data, we identified men with invasive breast cancer between 2010 and 2014 with known estrogen receptor and progesterone receptor (together HR) status and human epidermal growth factor receptor 2 (HER2) status. Tumor subtypes were classified as: HR+/HER2-, HR+/HER2+, HR-/HER2+ and triple negative (TN). We examined tumor subtypes by patient (pt) characteristics and performed multivariate Cox proportional hazards analyses to determine the associations of each variable with OS and BCSS. Results: We included 1508 pts with a median follow-up of 24 months (range 0-60). Median age was 65 years (range 26-97). At diagnosis, 86.6% of tumors were ductal, 97.1% HR+, 42.1% T1, 55.7% N0, 7.9% M1. Tumor subtype distribution was: 85.5% HR+/HER2-, 11.6% HR+/HER2+, 0.9% HR-/HER2+ and 2% TN. Compared with other subtypes, pts with TN tumors had higher grade disease, presented with more advanced stage and died more often from breast cancer (all p<0.0001); whereas pts with HR+/HER2- tumors were older (p=0.02) and more often white (p=0.02). In univariate analysis, OS at 5 years for all HER2- and all HER2+ was 74.2% and 64.1%, respectively (p=0.002); while BCSS at 5 years for all HER2- and all HER2+ was 88.4% and 78.8%, respectively (p=0.009). Of all subtypes, TN had the worst OS and BCSS (p<0.0001). Breast cancer was the cause of death in 43.7% of HR+/HER2-, 54.2% of all HER2+ and 100% of TN (p<0.0001). In multivariate analyses for OS, older pts (Hazard ratio [HaR] 3 vs. <50 years; p=0.001), stage IV (HaR 9 vs. stage I; p<0.001), HR+/HER2+ tumors (HaR 1.9 vs. HR+/HER2-; p=0.003), TN tumors (HaR 8.5 vs. HR+/HER2-; p<0.001) and unmarried pts (HaR 1.9 vs. married; p=0.002) had significantly worse survival. In multivariate analyses for BCSS, stage IV (HaR 25.7 vs. stage I; p<0.001), HR+/HER2+ tumors (HaR 2.1 vs. HR+/HER2-; p=0.019), TN tumors (HaR 17 vs. HR+/HER2-; p<0.001) and unmarried pts (HaR 2.2 vs. married; p=0.009) had significantly worse survival. Conclusion: We observed significant differences in outcomes by tumor type in men with breast cancer which mirror those previously observed for women with breast cancer. Among the limited numbers of men with HER2+ and TN disease in our sample, outcomes were poor, suggesting possible under-treatment, aggressive tumor biology, and/or more advanced of disease at presentation. Studies to better understand the inferior survival for men with these subtypes are warranted and efforts to ensure appropriate treatment are paramount. Citation Format: Leone J, Freedman RA, Zwenger AO, Lin NU, Tolaney SM, Vallejo CT, Leone BA, Winer EP, Leone JP. Tumor subtypes and survival in male breast cancer: SEER 2010-2014 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-19-02.