The Failure Patterns of Nasopharygeal Carcinoma After Intensity-Modulated Radiotherapy and Implications for Surveillance.

Objective: To investigate the treatment outcomes, failure patterns and surveillance strategy in patients with nasopharyngeal carcinoma (NPC) after intensity-modulated radiotherapy (IMRT). Methods: A cohort of patients with NPC who had received the full course of IMRT between 2008 and 2012 were retrospectively analyzed. The failure patterns, time to recurrence, and detection methods were recorded. The survival was calculated using the Kaplan-Meier method. Multivariate proportional hazard regression models were used to test the prognostic factors. Results: In total, 2607 patients with NPC treated with IMRT were recruited. After the median follow-up of 112 months, 402 (15.4%) patients experienced distant metastasis, 225 (8.6%) patients had local recurrence, and 77 (3.0%) patients had regional recurrences. The 10-year overall survival (OS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) rates were 74.5%, 90.1%, and 79.3%, respectively. The factors of male sex, age >50 years, lactate dehydrogenase >245 IU/L, advanced T classification, and advanced N classification were associated with poor OS. The N disease classification was the most important factor in predicting distant metastasis, and advanced T disease classification for high risk of local recurrence. For patients with T1 disease, the incidence of local recurrence was less than 2%, and the incidence of distant metastasis was less than 5% for patients with N0 disease. About 83% of the recurrence occurred in the first 5 years, and 20% of the recurrences showed no symptoms. Conclusion: High rate of local-regional control can be achieved for patients with NPC after IMRT, while distant metastasis remains as the major cause of failures. Patients with advanced N classification has high risk to develop distant metastasis, and most occurred within 5 years. Developing rational and individualized surveillance strategies based on the high risk factors of recurrence is helpful to balance the survival benefit and medical cost.