Background: Breast cancer is the second most prevalent type of cancer and the 
most common cancer among women. The gold standard in the treatment of 
breast cancer is postoperative radiation following breast-conserving surgery 
(BCS). The optimal timing to begin postoperative radiation therapy (RT) is still 
up for debate. 
Objective: The purpose of the study is to determine if the gap between BCS and 
postoperative RT has any impact on the frequency of local or distant relapses 
and overall survival in female patients with breast cancer.
Patients and Methods: Following the scheduling of radiation, we split the 302 
female patients into two groups: ≤180 days and >180 days, and retrospectively 
examined the clinical data. The Fisher exact test, the χ2test or dummy variables 
were used to determine if the two groups had an unbalanced distribution of 
prognostic and treatment variables. The Kaplan-Meier survival analysis and a 
restricted mean survival time (RMST) were used to assess local relapse-free 
survival (LRFS), distant metastasis-free survival (DMFS), and overall survival 
(OAS). After correcting for known confounding variables, multivariate Cox 
regression was performed to test for the independent effect of time of RT. The 
typical median time of follow-up was 6.5 years.
Results: There were statistically significant differences in the distribution of 
pathological stage, chemotherapy regimens, timing of the initiation of 
chemotherapy (neoadjuvant or adjuvant), and total dose of radiation. We were 
unable to find a relation between the time interval and the probability of local 
relapse at the 6.5-year median time of follow-up (p = 0.285 and 0.259) in both 
the univariate and multivariate analyses. When radiation was begun later than 
recommended, the DMFS and OAS univariate analyses revealed no influence on 
outcome (p = 0.3445 and p = 0.249, respectively), and the multivariate analysis 
supported this finding (p = 0.578 and p = 0.487, respectively).
Conclusion: Our findings demonstrate that there is no relationship between the 
scheduling of postoperative RT and the chance of local relapse, distant 
metastasis, or progression of overall survival in our groups.