Long-term outcomes of preoperative radiotherapy in locally advanced breast cancer: Analysis of Surveillance, Epidemiology, and End Results (SEER) database.

Abstract

e12600 Background: Currently the treatment paradigm for locally advanced breast cancer (LABC) is multimodality therapy with neoadjuvant systematic treatment, surgery and postoperative radiation therapy (RT). However, with improving outcomes from systematic therapy, the survival rates remain unpromising, which leads to the investigation of the concept of preoperative RT in LABC due to the potential advantages including a possible tumor downstaging and better cosmetic outcomes. We evaluated the overall survival (OS) and breast cancer specific survival (BCSS) of preoperative versus postoperative RT in LABC patients. Methods: Patients diagnosed with non-inflammatory LABC (defined as T3 N1, T4 N0, any N2 or N3, and M0) who received RT before or after surgery between 2010 and 2015 were identified using the SEER database. OS and BCSS were analyzed using Kaplan-Meier method and multivariate Cox proportional hazards model. Results: Among 19249 patients with LABC, 140 (0.7%) received preoperative RT and 19109 (99.3%) received postoperative RT. Overall, 5-year survival and BCSS are 59% and 63% in the preoperative RT group while 77% and 80% in the postoperative RT group. In all patients, treatment with preoperative RT was significantly associated with poor OS (HR 1.82, 95%CI 1.25 to 2.45, P < 0.001) and BCSS (HR 2.00, 95%CI 1.46 to 2.73, P < 0.001) after adjustment for other clinically relevant factors. However, there were no significant difference in terms of both OS and BCSS in ER+ (OS: HR 1.44, 95%CI 0.91 to 2.27, P = 0.12; BCSS: HR 1.55, 95%CI 0.94 to 2.54, P = 0.08) and HER2+ patients (OS: HR 1.33, 95%CI 0.55 to 3.22, P = 0.53; BCSS: HR 1.64, 95%CI 0.67 to 3.97, P = 0.28). Conclusions: Overall, preoperative RT in LABC may reduce overall survival and breast cancer specific survival. However, OS and BCSS were independent of radiation sequence for ER+ and HER2+ patients. This finding warrants further exploration of potential mechanisms of the disparity and the definitive role of preoperative RT in the multimodality therapy of LABC patients.