Comparison of Clinicopathologic Features and Outcomes Between Synchronous and Metachronous Bilateral Breast Cancer

Abstract

Purpose: Bilateral breast cancer (BBC) can be divided into two concurrent lesions, depending on the time of occurrence of primary cancer and secondary tumors after treatment of the primary cancer. This study aimed to compare the clinicopathological characteristics and results of synchronous BBC (SBBC) and metachronous BBC (MBBC).Methods: Data of patients diagnosed with breast cancer at Wonkwang university Hospital between October 1991 and October 2021 were retrospectively reviewed. Data of 3,259 patients who were diagnosed with malignant neoplasm of the right or left breast were reviewed. The tumor was defined as SBBC when another cancer was identified as BBC simultaneously or within six months after the primary breast cancer, and as MBBC when another cancer was identified after six months. Among patients with BBC, 31 had SBBC and 32 had MBBC.Results: In SBBC patients, the median age was 59.9 years, and the condition was diagnosed 3.3 years later compared with MBBC. The primary and secondary tumors of SBBC had lower disease stage, even when diagnosed late. Except for tumor, node, and metastasis stage, MBBC showed more invasive ductal carcinoma, while SBBC showed relatively more ductal carcinoma <i>in situ</i> in both primary and secondary tumors compared with MBBC. In addition, SBBC showed lower hormone receptor positivity rates and Ki-67 levels compared with MBBC. MBBC patients showed a higher survival rate compared with SBBC patients. MBBC is associated with higher overall survival rate compared with SBBC, and its prognosis is not worse compared with that of unilateral breast cancer. In the case of secondary tumor that develops in the contralateral breast without evidence of metastasis, the survival rate is similar to that of unilateral breast cancer, while the treatment is similar to that of primary tumor.Conclusion: As those with SBBC have a worse survival, these patients will require more medical attention; meanwhile, MBBC requires an active treatment approach that is equivalent to that for unilateral breast cancer.