Delay in initiating postmastectomy radiotherapy is associated with inferiorsurvival outcomes for locally advanced breast cancer patients treated with neoadjuvant chemotherapy and mastectomy

Objective: To evaluate the effect of surgery-radiotherapy interval (SRI) on clinical prognosis of locally advanced stage c II-III breast cancer patients treated with neoadjuvant chemtherapy and modified radical mastectomy. Methods: Clinical data of 1087 breast cancer patients treated with neoadjuvant chemotherapy and modified radical mastectomy from 11 hospitals in China were retrospectively analyzed. The optimal threshold value of SRI upon clinical prognosis was determined by maxstat method. The effect of SRI on clinical prognosis was evaluated by using multivariate Cox regression analysis and propensity score matching (PSM). Results: The median follow-up time was 72.9 months. The 5- year disease-free survival (DFS) and overall survival (OS) rates were 68.1% and 81.8%. All patients were divided into SRI ≤ 18 weeks (n = 917) and SRI > 18 weeks groups (n = 170). Multivariate Cox regression analysis demonstrated that hormone receptor status (P < 0.001), pathological T stage (P < 0.001), pathological N stage (P < 0.001) and SRI (P = 0.023) were independent influencing factors of DFS. Hormone receptor status (P = 0.013), pathological T stage (P = 0.006), pathological N stage (P < 0.001), endocrine therapy (P = 0.013) and SRI (P = 0.001) were significantly associated with OS. After balancing the clinical and pathological factors with PSM, patients with SRI < 18 weeks had superior DFS and OS to those with SRI > 18 weeks. Conclusions: SRI affects the clinical prognosis of locally advanced breast cancer patients treated with neoadjuvant chemotherapy and modified radical mastectomy. Radiotherapy should be performed within 18 weeks after mastectomy. (authors)