Abstract PO2-10-03: Clinical characteristics and survival trends of male breast cancer in the United States: A propensity score matched analysis
Authors: Roy Arya Mariam , George Anthony , Patel Archit , Alharbi Malak , Attwood Kristopher , Gandhi Shipra 
Published: May 2024

Abstract
Introduction Male breast cancer (MBC) is extremely rare and represents less than 1% of breast cancer (BC). There are limited studies investigating clinical outcomes of MBC. Although the survival of female breast cancer (FBC) has increased over the years; there is a substantial knowledge gap regarding survival trends of MBC. Given the rarity of MBC, recommendations on the treatment of MBC are scarce and mainly extrapolated from the data from FBC. We aim to analyze the clinical characteristics and annual trend in the survival of MBC compared to FBC. Methods We queried the National Cancer Database for BC patients (pts) diagnosed during 2004-2020. The demographic, clinicopathological and treatment characteristics were summarized by sex. An inverse-propensity weighted cox regression model was used to assess the association between sex and overall survival. Propensity weights were based on age, race, insurance, T, N, M-stages, subtype, grade, chemotherapy (CT), radiation (RT), hormone therapy (HT), and time to definitive treatment. To compare survival trends over time, year of diagnosis and its interaction with sex were included in the model. All analyses were performed at a significance level of 0.05. Results A total of 24, 055 MBC and 2,532,470 FBC pts were identified. MBC pts were older (mean age: 65.6 vs 61.4 years), Blacks (12.8 vs 11.2%) and had more government insurance (55.7% vs 45.8%) compared to FBC (all p&lt; 0.001). Compared with FBC, more MBC pts had stage IV (7% vs 4.7%), fewer pts had stage I (33.4% vs 44.8%), more pts had larger tumors (cT4: 6% vs 3.7%), and node positive disease (18.5% vs 15.5%) (all p&lt; 0.001). MBC were more likely estrogen (ER) (88.5% vs 78.5%) and progesterone receptor (PR) (79.6% vs 68%) positive and less likely HER2 receptor positive (7.9% vs 9.3%) or triple negative (2.8% vs 7.6%) compared to FBC (all p &lt; 0.001). Male pts with BC received less CT (38.7% vs 41.2%), RT (32% vs 52.6%), HT (59.8% vs 62.5%) compared to females with BC (p &lt; 0.001). The overall survival (OS) rates were lower in MBC compared to FBC (5-year: 73% vs 83%; 10-year: 54% vs 70%, p &lt; 0.001). In the propensity weighted cox-regression model, males had higher mortality compared to females with BC (HR 2.8, 95% CI 2.88 - 2.9, p &lt; 0.001). This difference in OS was observed in TNBC (HR 1.2, 95% CI 1.21 - 1.24) and HER2+ (HR 2, 95% CI 1.9 - 2.0), but not in ER/PR+ HER2- BC (HR 0.78, 95% CI 0.78 - 0.79), all p &lt; 0.001. The 5-year and 10-year OS of early-stage MBC and advanced MBC was lower compared to FBC (Early-stage:- 5-year: 77% vs 86%, 10-year: 57% vs 72%, HR 2.9, 95% CI 2.9-2.92; Advanced: 5-year: 23% vs 28%, 10-year: 8% vs 13%, HR 1.14, 95% CI 1.14 – 1.2, both p &lt; 0.001) The 5-year OS rates increased steadily for FBC from 2004-2015; however, the survival rates were not improved for MBC (Table 1) (p-value for interaction of sex and year of diagnosis was 0.02). Conclusion MBC pts have higher mortality rates and poor clinical outcomes compared to FBC pts. We demonstrate that the survival of MBC pts has not improved over the last decade, even after adjusting for clinicopathological and treatment characteristics. These findings suggest the need to investigate personalized treatment interventions for male breast cancer pts, especially given the disparate trends in survival among male and female BC over a period of time.
Table 1: Survival trend by sex - overall BC cohort
Citation Format: Arya Mariam Roy, Anthony George, Archit Patel, Malak Alharbi, Kristopher Attwood, Shipra Gandhi. Clinical characteristics and survival trends of male breast cancer in the United States: A propensity score matched analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-10-03.