Clinicopathological Characteristics, Treatment and Outcome of 123 Patients with Synchronous or Metachronous Bilateral Breast Cancer in a Swiss Institutional Retrospective Series

To evaluate the prognosis, the patient and tumor characteristics, and the treatment of bilateral breast cancer (BBC) and to compare synchronous (sBBC) and metachronous BBC (mBBC). For this retrospective study, data from 123 consecutive BBC patients (56 sBBC and 67 mBBC) that were presented at the Sion Hospital tumor board between 2007 and 2018 were collected retrospectively. Mean follow-up was 85 months. 2 tumors in both groups were more often diagnosed radiologically. Mean time interval between mBBC was 115 months. A shorter interval was positively correlated with a negative hormonal receptor (HR) status and higher grade for the 2 tumor. There was no difference in overall survival (OS) and relapse-free survival (RFS) between sBBC and mBBC. OS was longer if both tumors were hormonal receptor (HR) positive. mBBC exhibited a higher local recurrence rate than sBBC (p=0.03). sBBC and mBBC patients did not show any difference in OS or RFS, although mBBC patients were more prone to local relapses.