Timing of RT initiation does not improve long-term outcome in breast cancer
Starting radiation therapy (RT) shortly after breast-conserving surgery (BCS) does not appear to yield improvements in long-term outcome, bringing into question the common position that RT should be initiated as soon as possible following surgery so as to increase treatment efficacy in breast cancer patients, according to a recent study.
The study included two cohorts of women with primary invasive stage I to IIIA breast cancer and treated with BCS+RT. Cohort 1 (n=2,759) excluded patients receiving chemotherapy before RT, and analysis was stratified according to the use of adjuvant systemic therapy (AST). Cohort 2 (n=1,120) comprised patients who received chemotherapy, and analysis was performed by comparing chemotherapy before (BCS-chemotherapy-RT) and after RT (BCS-RT-chemotherapy).
The primary endpoint was disease-free survival (DFS), as estimated using multivariable Cox regression. Locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were also evaluated as secondary endpoints.
Cohort 1 showed better DFS and DMFS for a time interval of >55 vs <42 days. Patients who received AST had even higher DFS for >55 days (hazards ratio [HR], 0.60; 95 percent CI, 0.38 to 0.94) and for 42 to 55 days (HR, 0.64; 0.45 to 0.91) than for <42 days. A similar pattern of results was observed for DMFS, whereas timing had no effect on LRRFS and OS.
Among patients without AST, timing showed no association with DFS, DMFS and LLRFS. However, 10-year OS was notably lower for a time interval of 42 to 55 and >55 vs <42 days.
In cohort 2, timing did not influence survival among patients who received BCS-chemotherapy-RT. For those who had BCS-RT-chemotherapy, DMFS was higher for a time interval of >55 than <42 days.
The present data suggest initiating RT as soon as possible after BCS is not necessary as timing does not improve survival rates, researchers said. It is important that patients are informed about this to prevent them from worrying about tumour growth and worse outcomes in case of a longer time interval between BCS and RT.