Clinicopathological characteristics, treatment patterns, and prognosis of male breast cancer: China versus the United States.
Authors: Gao Yuxuan , Zhang Mengmeng , Shao Nan , Shan Zhen , Zhang Yunjian , Jiang Zefei , Lin Ying 
Published: June 2023

e13543

Background: Male breast cancer (MBC) is a rare disease. There have been several relatively large-scale MBC retrospective studies based on the National Cancer Database (NCDB) and the Surveillance Epidemiology and End Results (SEER) database, both of which recorded the information about American patients. However, relevant studies in China are still very scarce. We aimed to explore the characteristics and prognostic information of Chinese MBC patients from a more comprehensive perspective by comparing them with US patients. Methods: We identified 912 male patients who received breast cancer diagnosis between 1988 to 2022 from 31 centers in total and extracted their clinicopathological, therapeutical and prognostic information from Chinese Society of Clinical Oncology database and other cooperative centers in China. The corresponding information about US patients from the same period were also extracted from the SEER database. Our analysis finally included 883 Chinese and 3751 US patients. Kaplan-Meier curves, log-rank test and the Cox proportional hazards regression models were used to analyze and compare survival and identify prognostic factors. Results: Comparing with US MBC patients, Chinese patients showed a younger age (median age group 55 - 64 years in China vs 65 - 74 years in US, P<0.001) but more advanced AJCC stages (18.2% vs 14.5% in stage III and 7.7% vs 7.4% in stage IV, P<0.001). The majority of patients from both countries were ductal carcinoma (infiltrative and in situ) and luminal type. Chinese MBC patients were more likely to receive mastectomy (88.2% vs 58.4%, P<0.001) and chemotherapy (49.5% vs 33.0%, P<0.001). About 63.3% of Chinese patients received endocrine therapy, which was not recorded in SEER database. Chinese patients also showed a better prognosis both in 3-year (91.9%, 95% CI 89.7% - 94.1% vs 79.2%, 95% CI 77.9% - 80.6%) and 5-year (85.0%, 95% CI 81.9% - 88.2% vs 67.3%, 95% CI 65.7% - 68.9%) overall survival rates. Multivariate Cox model confirmed that age (P<0.001, HR=1.034, 95% CI 1.018 - 1.051), AJCC stages (comparing with stage I, P=0.894 for stage II; P=0.038, HR=1.963, 95% CI 1.037 – 3.717 for stage III and P<0.001, HR=4.001, 95% CI 2.035 – 7.868 for stage IV), mastectomy (P=0.002, HR=0.357, 95% CI 0.184 - 0.692) and endocrine therapy (P<0.001, HR=0.373, 95% CI 0.245 - 0.570) were independent prognostic factors of overall survival for Chinese MBC patients. Conclusions: With the largest scale for MBC patients so far in China, our findings revealed the exclusive features of Chinese MBC patients, who were diagnosed at a younger age, more advanced in AJCC stages, more conservative in surgery selection, more chemotherapy use and higher in 3-year and 5-year overall survival rates than their US counterpart. We also identified that age, AJCC stages, mastectomy and endocrine therapy were independent prognostic factors for overall survival of MBC patients in China.