Do we need reshape rTNM staging system for ipsilateral breast tumor recurrence of breast cancer? A population-based, propensity score matched cohort study

The aim of the study was to explore the role of recurrent TNM (rTNM) staging in predicting prognosis for ipsilateral breast tumor recurrence (IBTR) and determine the optimal treatment strategy for IBTR.

IBTR cases were identified from the Surveillance, Epidemiology, and End Results (SEER) database spanning the years 2000–2018. Cox proportional hazards analysis was performed to examine factors associated with overall survival (OS) and breast cancer-specific survival (BCSS). Propensity score matching (PSM) was employed to match IBTR with primary early breast cancer (EBC) based on clinicopathological characteristics. Investigations into the impact of different therapies were also included.

Of the 4375 IBTR cases included in the study, the 5-year OS was 87.1%, 71.6% and 58.7% in rTNM stages I, II and III, respectively. After PSM, while IBTR patients had worse survival to primary EBC patients, prognosis of IBTR for different rTNM stage always closely aligned with the corresponding stage of primary EBC. Repeat breast-conserving surgery (BCS) with radiation therapy was equivalent to mastectomy with respect to OS and BCSS. Chemotherapy was favorable for OS and BCSS in estrogen receptor (ER)-negative IBTR or IBTR occurring within a 60-month interval.

rTNM staging system has an outstanding prognostic value for survival outcome of patients with IBTR, and IBTR and primary EBC may have potentially analogous features in the context of TNM staging. BCS plus radiation therapy may be an alternative. IBTR cases who have experienced recurrence with short intervals and with ER-negative tumors might benefit from chemotherapy.