A comparative clinicopathological and survival analysis of synchronous bilateral breast cancers

The present study aimed to explore the clinicopathological characteristics, potential heterogeneity and prognostic factors in synchronous bilateral breast cancer (SBBC).

We performed a retrospective review and paired comparison of the clinicopathological characteristics of 114 patients with SBBC in the Peking Union Medical College Hospital from January 2008 to September 2019. The prognostic significance of triple negativity status and coexistence ductal carcinoma in situ (DCIS) with bilateral invasive ductal carcinomas of no special type (IDC-NST) was analyzed in SBBC.

Most bilateral lesions on both sides were of IDC-NST, grade 2, luminal subtype, and stage I. Although most lesions were concordant between the left and right side, discordances were observed in histological type (25 cases, 21.9%), histological grade (31 cases, 27.2%), pTNM (61 cases, 53.5%), molecular subtypes (20 cases, 17.5%), and immunohistochemical staining of ER (18 cases, 15.8%), PR (26 cases, 22.8%), and HER2 (12 cases, 10.5%). Moreover, there was no significant difference in disease-free survival (DFS) and overall survival (OS) between IDC-NST with coexisting DCIS on both sides and IDC-NST with coexisting DCIS on one side or pure IDC-NST. SBBC with triple negativity on both sides exhibited a significantly shorter DFS and OS when compared with triple negativity on one side or non-triple negativity on both sides (p<0.001), and remained an independent prognostic factor by multivariate analysis.

A considerable proportion of discordance in clinicopathological characteristics is observed in SBBC, supporting the necessity of comprehensive pathological examination including immunohistochemical testing on both sides in clinical practice. Moreover, SBBC with triple negativity on both sides is a prognostic for poor survival.