Clinical Characteristics and Survival Trends of Male Breast Cancer in the United States: A Propensity Score Matched...

Background: Male breast cancer (MBC) is extremely rare, representing less than 1% of breast cancer (BC). Owing to the rarity, there is a substantial knowledge gap regarding the survival trends of MBC compared with female breast cancer (FBC). Methods: We queried the National Cancer Database for BC patients diagnosed during 2004-2018 and utilized an inverse propensity weighted cox regression model assessed the association between sex and overall survival (OS) and survival trends over time by sex. Results: We identified 24,055 MBC and 2,532,470 FBC patients. Patients with MBC were older (mean age: 65.6 vs. 61.4 years), and more likely to have stage IV at diagnosis (7% vs. 4.7%), larger tumors (cT4: 6% vs. 3.7%), and node-positive disease (18.5% vs. 15.5%) (p < 0.001) compared with FBC. MBC were more likely to be estrogen (ER) (88.5% vs. 78.5%) and progesterone receptor (PR) (79.6% vs. 68%) positive and less likely to be HER2 receptor positive (7.9% vs. 9.3%) or triple negative (2.8% vs. 7.6%) compared with FBC (all p < 0.001). The OS rates were lower in MBC compared with FBC (5-year: 73% vs. 83%; 10-year: 54% vs. 70%, p < 0.001). In the propensity weighted cox-regression model, males had higher mortality than females with BC (HR 2.8, 95% CI 2.88-2.9, p < 0.001). The 5-year OS rates increased steadily for FBC from 2004-2015; however, the survival rates did not improve for MBC over the last decade. Conclusions: Our study shows that MBC patients continue to have poor OS compared with patients with FBC and no significant improvement in survival of MBC patients over the past decade. These results underscore the need to investigate personalized treatment interventions for patients with MBC to improve outcomes.