Clinical characteristics and clinicopathological correlations of bilateral breast cancer in China: A multicenter study from Chinese Society of Breast Surgery (CSBrS-006).

Objective To investigate the clinical characteristics and clinicopathological correlations of bilateral breast cancer (BBC) in China. Methods Data of 440 patients diagnosed with BBC in 2018 were collected from 33 centers of the Chinese Society of Breast Surgery. Demographic characteristics, bilateral tumor characteristics, and comprehensive treatment data were obtained. Correlations between the clinicopathological characteristics of bilateral tumors were analyzed. Results The proportion of BBC was 0.22%-3.08%. A total of 33 (7.5%) patients had a family history of malignant tumors, 304 (69.1%) patients had synchronous BBC. Only 1 (0.2%) patient was male. More than half of all patients received concurrent or asynchronous endocrine/chemotherapy, 32.5% of all human epidermal growth factor receptor 2 (HER2)-positive patients received HER2-targeted therapy, and approximately 21.6% of all patients received radiotherapy. The most common pathological cancer type was invasive ductal cancer (>60%). Approximately 70% of all patients had bilateral hormone receptor (HR)-positive tumors and presented with a single breast mass. Significant correlations were found with pathological type, histological grade, locations of tumor, molecular subtype, Ki-67 index, tumor site and size of bilateral tumors. Results of the subgroup analysis showed more clinicopathological characteristics when synchronous BBC was compared with metachronous BBC. Conclusions In China, the clinicopathological characteristics of bilateral tumors showed significant correlations, and more significant clinicopathological correlations were observed when synchronous BBC was compared with metachronous BBC.