Induction chemotherapy plus re-irradiation versus re-irradiation alone in locally recurrent nasopharyngeal carcinoma: A model-based analysis.

OBJECTIVE:To investigate the role of additional induction chemotherapy (IC) prior to re-irradiation in locally recurrent nasopharyngeal carcinoma (lrNPC). METHODS:A total of 480 patients from three cancer treatment centers who received re-irradiation between 2012 and 2020 were retrospectively analyzed. Overall survival (OS) was determined using the Kaplan-Meier method and compared with log-rank method. Inverse probability of treatment weighting (IPTW) was performed to match the patients in pairwise treatment groups. Multivariate analysis using the Cox proportional hazards regression method identified predictors of OS. The risk stratification model was defined by the risk score calculated with the sum of coefficients. RESULTS:In the entire cohort, the addition of IC was associated with similar OS compared with radiotherapy alone (P = 0.58) or with concomitant chemoradiation (P = 0.76). A risk stratification model was constructed and validated based on significant prognostic factors (coefficient) including male (0.6), age ≥ 60 years (0.9), volume of recurrence gross tumor volume ≥ 16 cc (0.7), and lactate dehydrogenase (LDH)-ratio ≥ 0.5 (0.4). In the intermediate-risk group (sum of coefficient: 0.9---1.6), patients with IC plus re-irradiation had a significantly better OS than those who received re-irradiation (P = 0.03). After adjustments for several potentially confounding variables with IPTW, survival benefit of IC was also observed (P = 0.031). However, no significant difference in OS for the additional IC prior to re-irradiation was demonstrated in the low- (sum of coefficient: <0.9) and high-risk group (sum of coefficient: > 1.6). CONCLUSION:Additional IC prior to re-irradiation was associated with improved OS in the intermediate-risk group of lrNPC, whereas there was no difference for the low-risk and high-risk group. Prospective validation is required to validate these findings.