Radiotherapy interruption due to holidays adversely affects the survival of patients with nasopharyngeal carcinoma: a joint analysis based on large-scale retrospective data and clinical trials.

BACKGROUND: The impact of radiotherapy interruption due to the Spring Festival holidays in China on the survival of patients with nasopharyngeal carcinoma (NPC) is unclear. METHODS: Nontrial patients with locoregionally advanced NPC receiving radiotherapy plus induction chemotherapy (IC) and/or concurrent chemotherapy (CC) were included (N = 5035) and divided into two groups based on the Spring Festival-induced radiotherapy interruption. Kaplan-Meier curves for overall survival (OS) and failure-free survival (FFS) were compared between rival groups. Impact of the timing of radiotherapy interruption (during or outside the Spring Festival) on survival was investigated in a propensity score-matched dataset. We adopted ordination correspondence analysis to determine the cut-off of radiotherapy prolongation for prognostic prediction, and accordingly performed subgroup analysis based on delayed days and chemotherapy details. Individual patient data of three phase III NPC trials (NCT00677118, NCT01245959, NCT01872962) were used for validation (N = 1465). RESULTS: Radiotherapy interruption was most frequently observed between December to January of the following year. Significantly lower OS and FFS were associated with the Spring Festival-induced interruption of radiotherapy (P = 0.009 and 0.033, respectively), but not that interruption of IC. In two matched comparison groups, the timing of radiotherapy interruption during the Spring Festival was more likely to lead to a decrease in FFS than outside the Spring Festival (P = 0.046), which was not observed in the validation using clinical trial data or in the subgroup analysis based on the 5-day delayed time. The absence of CC and the accumulated dose of cisplatin < 200 mg were related to the negative influences of the Spring Festival-induced radiotherapy interruption on FFS (P = 0.002) and OS (P = 0.010), respectively. CONCLUSIONS: The poor survival of patients with NPC is associated with the Spring Festival-induced interruption of radiotherapy. We recommend that these patients receive adequate doses of cisplatin concurrently with radiotherapy.