Long-term efficacy and adverse effects of intensity-modulated radiotherapy for nasopharyngeal carcinoma

Objective: To investigate the long-term efficacy and adverse effects of intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: A total of 869 patients with biopsy-proven NPC without distant metastasis who underwent the whole course of IMRT from 2009 to 2010 were enrolled. Of all the patients, 84.8% received cisplatin-based chemotherapy. The prescribed dose to the primary lesion in the nasopharynx was 66-70 Gy in 30-32 fractions, and the dose to the positive lymph nodes in the neck was 66 Gy in 30-32 fractions. The Kaplan-Meier method was used to calculate survival rates, the log-rank test was used for difference analysis and univariate prognostic analysis, and the Cox proportional hazards model was used for multivariate prognostic analysis. Results: The 5-year overall survival(OS), local recurrence-free survival, regional recurrence-free survival, distant metastasis-free survival, and disease-free survival (DFS) were 84.0%, 89.7%, 94.5%, 85.6%, and 76.3%, respectively. In the patients with locally advanced NPC, concurrent chemotherapy tended to reduce distant metastasis (83.6% vs. 75.7%, P = 0.050) and improve OS (82.6% vs. 77.0%, P = 0.082). Induction chemotherapy tended to improve OS (80.7% vs. 71.4%, P = 0.057), and the induction chemotherapy containing docetaxel or gemcitabine tended to improve OS (83.3% vs. 72.2%, P = 0.058). The patients who received a boost after the initial radiotherapy had a significantly lower DFS rate than those who did not (52.2% vs. 71.1%, P = 0.004). The concurrent chemotherapy increased the incidence rates of long-term xerostomia and trismus, while a high dose of cisplatin increased the incidence rates of xerostomia and hearing impairment. Conclusions: IMRT for NPC provides satisfactory long-term efficacy. Concurrent chemotherapy combined with IMRT tends to reduce the incidence of distant metastasis, and other values need further investigation. The boost therapy after radiotherapy may be associated with poor prognosis. Chemotherapy increases the incidence of long-term toxicities. (authors)