Superiority of intensity-modulated radiation therapy in nasopharyngeal carcinoma with skull-base invasion

Purpose To compare the clinical results and functional outcomes between two-dimensional conventional radiation therapy (2DRT) and intensity-modulated radiation therapy (IMRT) in nasopharyngeal carcinoma (NPC) with skull-base invasion. Methods A total of 1258 patients were subclassified into two groups: mild skull-base invasion group (792; 63%) and severe skull-base invasion group (466; 37%). Patients were pair matched (1:1 ratio) using six clinical factors into 2DRT or IMRT groups. The Kaplan-Meier method and Cox regression model were performed to assess overall survival (OS), disease-free survival (DFS), locoregional relapse-free survival (LRRFS) and distant metastasis-free survival (DMFS). Toxicities were evaluated. Results IMRT significantly improved four-year OS compared with 2DRT (65.6% vs. 81.8%, P = 0.000), DFS (57.3% vs. 73.3%, P = 0.000) and LRRFS (76.5% vs. 87.5%, P = 0.003) in NPC with severe skull-base invasion, but similar results were observed in patients with mild skull-base invasion (P > 0.05). In patients with severe invasion, radiation therapy techniques were found to be an independent prognostic factor for OS (HR = 0.457, P = 0.000), DFS (HR = 0.547, P = 0.000) and LRRFS (HR = 0.503, P = 0.004). IMRT was associated with better OS. In subgroups analysis, IMRT group also had a better survival in OS, DFS (P < 0.05 for all rates) for patients received concurrent chemotherapy and sequential chemotherapy compared to 2DRT in the severe invasion group. The IMRT group displayed lower incidence of mucositis, xerostomia, trismus (< 1 cm) and temporal lobe necrosis than the 2DRT group. Conclusions IMRT significantly improved patient survival compared with 2DRT in NPC patients with severe skull-base invasion, but a similar survival rate was noted in mild invasion patients. Chemotherapy can improve survival in NPC patients with severe invasion. Among the two therapies, IMRT significantly decreased therapy-related toxicity.