Exploring the Impact of Delayed Postoperative Radiotherapy on Relapse and Metastasis in Female Breast Cancer Patients: Insights from Penalized Cox Regression.

Introduction: The correlation between the timing of radiotherapy commencement following breast surgery and the disease - free status of patients remains a topic of debate. In this study, we investigated the association between the delay in adjuvant radiotherapy post - surgery and the survival free from relapse or metastasis in women with breast cancer, considering the substantial presence of censored data. Methods: Conducted as a historical cohort investigation, this study involved 284 individuals diagnosed with breast cancer who underwent surgical procedures between 2001 and 2007 and were subsequently monitored until March 2017. The research delved into the relationship between the interval separating radiotherapy and surgery, along with various demographic and clinical factors, and the incidence of local relapse or metastasis in breast cancer. This analysis was carried out using penalized Cox regression modeling, and the acquired data were subjected to analysis using R 3.6.3. Results: A total of 284 women, with a mean age of 47.2 ± 11.3 years, fulfilled the inclusion criteria for this study. The maximum follow - up period extended to 11.1 years, with the duration between surgery and radiotherapy averaging 168 ± 84.3 days. Approximately 10% of the patients encountered local relapse, and 19% experienced metastasis. In a comprehensive analysis of factors influencing disease - free survival, the disease stage emerged as a significant factor, while the interval between surgery and radiotherapy (=180 days vs. >180 days) did not exhibit any significant impact on the hazard of failure. Furthermore, the analysis of delays in radiation therapy lasting 3, 4, or 5 months did not reveal any significant effects. Conclusions: In the studied patients, the delay in radiotherapy initiation after surgery did not lead into outcomes of local relapse or metastasis. [ABSTRACT FROM AUTHOR]