Appropriate Timing of Radiotherapy After Mastectomy for High-Risk Breast Cancer
Posted: Monday, November 22, 2021
Siye Chen, MD, PhD, of the Cancer Hospital & Institute, Chinese Academy of Medicine Sciences, Beijing, and colleagues conducted a study to determine the proper timing of radiotherapy after mastectomy and chemotherapy in patients with high-risk breast cancer. Presented during the 2021 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 70), these data suggest that a delay in radiotherapy initiation may be correlated with poor oncologic outcomes. Thus, they recommend that such radiotherapy be initiated within 40 days after chemotherapy and 165 days after mastectomy.
This open-label, phase III trial enrolled 584 patients with stage II to III breast cancer who underwent mastectomy followed by chemotherapy and radiotherapy. At the median follow-up of 83.5 months, the median interval from surgery to radiotherapy was 168 days, and the interval from chemotherapy to radiotherapy was 27 days. The 8-year disease-free survival rate was significantly lower for a surgery-to-radiotherapy interval of more than 165 days compared with than 165 days or less (P = .019), whereas the rate of distant metastasis was significantly higher (P = .031). Additionally, participants with a surgery-to-radiotherapy interval of more than 180 days demonstrated a significantly lower overall survival rate compared with those who had a shorter interval (P = .012).
In addition, a chemotherapy-to-radiotherapy interval of more than 40 days was associated with a significant decrease in 8-year disease-free survival (P = .002) and overall survival (P = .002) rates compared with shorter intervals; a significant increase in distant metastasis was also observed (P = .001). When the investigators adjusted for prognostic variables, a surgery-to-radiotherapy interval of more than 165 days and clinical stage remained associated with poor disease-free survival and distant metastasis, whereas an interval of more than 180 days and clinical stage correlated with inferior overall survival. Notably, a chemotherapy-to-radiotherapy interval and clinical stage were independently associated with poor outcomes.
Disclosure: The study authors reported no conflicts of interest.