Impact of time to initiation of postoperative radiotherapy after neoadjuvant chemotherapy on the prognosis of breast cancer: A retrospective cohort study in China

The optimal time to the initiation of postoperative radiotherapy (TTR) in breast cancer patients after neoadjuvant chemotherapy (NAC) and surgery is unclear. We explored the association between TTR and outcomes among breast cancer females to determine the optimal timing for radiotherapy. We included 1022 women with breast cancer who underwent NAC and surgery between 1997 and 2019. Patients were categorized into three groups based on the TTR: <8 weeks, 8 to 16 weeks and >16 weeks. We used Cox proportional hazards models and analyzed the hazard ratios (HRs) for breast cancer-specific mortality (BCSM) and all-cause mortality (ACM). The median TTR for the cohort was 97 days. Compared to patients with TTRs of 8 to 16 weeks, those with TTRs 16 weeks had an increased risk of BCSM (HR, 2.59; 95% confidence interval [CI], 1.26-5.36 and HR, 2.01; 95% CI, 1.24-3.28, respectively) and ACM (HR, 2.32; 95% CI, 1.17-4.56 and HR, 1.92; 95% CI, 1.24-2.98, respectively) after adjusting for the confounders. Furthermore, at TTR of >16 weeks, each additional week of TTR was associated with a 3% increase in BCSM risk and 2% increase in ACM risk. Our findings suggest that patients who have undergone NAC and surgery show lower BCSM and ACM risks at TTR of 8 to 16 weeks compared to 16 weeks.