Comparison of the treatment outcomes of intensity-modulated radiotherapy and two-dimensional conventional radiotherapy in nasopharyngeal carcinoma patients with parapharyngeal space extension.

Objective: This study investigated the contribution of intensity-modulated radiotherapy (IMRT) to improved treatment outcome in patients with nasopharyngeal carcinoma (NPC) and parapharyngeal space (PPS) extension.

Methods: A total of 1052 cases with PPS extension were retrospectively reviewed, including 512 (48.7%) patients treated with two-dimensional conventional radiotherapy (2D-CRT) and 540 (51.3%) patients treated with IMRT.

Results: Significant differences in local relapse-free survival (LRFS) and overall survival (OS) (P<0.001, P<0.001, respectively), but not distant metastasis-free survival (DMFS; P=0.383), were observed between the 2D-CRT and IMRT groups in univariate analysis. The radiotherapy technique was found to be an independent prognostic factor for death (HR=0.674, 95% CI: 0.537-0.846, P=0.001) and local recurrence (HR=0.486, 95% CI: 0.324-0.727, P<0.001), but not for DMFS. IMRT improved local control in patients with carotid space (CS) involvement compared to 2D-CRT (P<0.001). LRFS was significantly different between patients with and without CS extension in the 2D-CRT group (P<0.001), but not in the IMRT group (P=0.215).

Conclusions: Compared to 2D-CRT, IMRT improved LRFS in patients with PPS extension, especially patients with CS extension, but did not improve DMFS. CS extension was not statistically prognostic for local control in NPC patients with PPS extension.