Impact of the weekday of the first intensity-modulated radiotherapy treatment on the survival outcomes of patients with nasopharyngeal carcinoma: A multicenter cohort study

Background: This study's purpose was to assess whether the weekday on which intensity-modulated radiotherapy (IMRT) is initiated influences survival outcomes in patients with nasopharyngeal carcinoma (NPC). Materials and methods: A total of 1440 patients with NPC who received IMRT were enrolled in this study between January 2010 and June 2016. The patients were divided into five groups according to the weekday of their first radiotherapy treatment. Group 1 (n = 322), Group 2 (n = 322), Group 3 (n = 286), Group 4 (n = 292) and Group 5 (n = 218) received first radiotherapy on Monday, Tuesday, Wednesday, Thursday and Friday respectively. Differences in the rates of overall survival (OS), disease-free survival (DFS), loco-regional relapse-free survival (LRRFS) and distant metastasis-free survival (DMFS) were compared among the five groups using the KaplanMeier method and Cox regression models. Results: No significant differences were found in OS, DFS, LRRFS or DMFS among the five groups. The Cox regression analysis showed that the weekday on which the radiotherapy was initiated was not an independent predictor of OS (Hazard Ratio [HR], 1.056; 95%CI: 0.959-1.164, P = 0.268), DFS (HR, 1.067; 95% CI: 0.980-1.161, P = 0.137), LRRFS (HR, 1.069; 95% CI: 0.914-1.249, P = 0.404) and DMFS (HR, 1.027; 95% CI: 0.929-1.134, P = 0.607). The subgroup analysis showed no significant differences among the five groups. Conclusions: This study showed that the day of the week that patients with nasopharyngeal carcinoma begin radiotherapy has no effect on their survival outcomes.