Long-term outcomes of intensity-modulated radiotherapy for 868 patients with nasopharyngeal carcinoma: an analysis of survival and treatment toxicities

Background and purpose: To evaluate the long-term survival outcomes and toxicity of NPC patients treated with intensity-modulated radiotherapy (IMRT).

Materials and methods: From May 2001 to October 2008, 868 non-metastatic NPC patients treated by IMRT were analyzed retrospectively. The Radiation Therapy Oncology Group (RTOG) criteria were used to assess toxicity.

Results: With a median follow-up of 50 months (range, 5-115 months), the 5-year estimated disease specific survival (DSS), local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS) and distant metastasis-free survival (DMFS) were 84.7%, 91.8%, 96.4% and 84.6%, respectively. Of the 868 patients, 186 (21.3%) developed failure after treatment. Distant metastasis was the major failure pattern after treatment. The 5-year OS rate in patients with stage I, II, III, and IVa-b were 100.0%, 94.3%, 83.6%, and 70.5%, respectively. The 5-year LRFS rate in patients with stage T1, T2, T3, and T4 disease were 100.0%, 96.0%, 90.4%, and 83.3%, respectively (χ(2) = 26.32, P<0.001). The 5-year DMFS for N0, N1, N2, and N3 patients were 96.1%, 85.6%, 73.7%, and 62.1%, respectively (χ(2) = 65.54, P<0.001). Concurrent chemotherapy failed to improve survival rates for patients with advanced locoregional disease. The most common acute toxicities were mainly in grade 1 or 2. Compared with IMRT alone, IMRT plus concurrent chemotherapy increased the severity of acute toxicities. The incidence of brain radiation damage was relatively high (5.5%, 48/868 cases), and was not observed in patients with stage T1-2.

Conclusion: IMRT for NPC yielded excellent survival outcomes, and distant metastasis was the most commonly seen failure pattern after treatment. The role of concurrent chemotherapy for advanced locoregional stage NPC patients needs to be further investigated. Treatment-related toxicities were well tolerable. However, the incidence of brain radiation damage was relatively high, especially for patients with advanced T-stage.