Importance: Prolonged time to treatment and interruptions in radiation therapy (RT) are important considerations for physicians and patients with nasopharyngeal carcinoma (NPC). The National Comprehensive Cancer Network (NCCN) recommends RT to start within 6 weeks of diagnosis, with minimal interruptions in treatment. However, the survival impact of delayed or prolonged treatment remains unknown.
Objective: To determine if delayed or prolonged treatment-related time intervals (TRTIs) would impact survival in patients with NPC. The TRTIs investigated were duration of radiation treatment (RTd), time to radiation start (TTR), and time to chemotherapy start (TTC).
Design, Setting, and Participants: In this observational cohort study, 3,893 patients with NPC were identified from the National Cancer Database (NCDB).
Exposures: Patients received concurrent chemoradiation (CCRT) of at least 66 cGy and radiation treatment time of at least 40 days.
Main Outcomes and Measures: Separate univariable Cox regression model was used to analyze OS as a function of TRTIs, as well as for each Charlson-Deyo Score, T stage, N stage, histological type, ethnicity, age, sex, and facility type. Upon finding significance at p < 0.05, the multivariable Cox regression analysis with backward elimination was performed to yield the final prediction model. Results were considered statistically significant when p < 0.05.
Results: RTd was significantly associated with OS while not adjusting for other factors (HR: 1.006, 95%CI=1.004-1.008, p<0.0001). However, RTd was not related to OS in the multivariable analysis (p=0.1884). The TTR and TTC variables were not associated with OS in the univariable analysis (p=0.8828, p=0.8812).
Conclusions and Relevance: TRTIs were not independently associated with OS in this cohort of NPC patients in the NCDB. Current NCCN guidelines recommend radiation within 6 weeks, and thus the evidence of non-adherence has to be further investigated. Future research into the association of TRTI with other disease outcomes, such as disease-free survival (DFS) and locoregional control (LRC), is needed.