Is atotal dose of 54Gy with radiochemotherapy sufficient for treatment of intermediate-risk volumes in nasopharyngeal cancer?

Abstract

The mainstay treatment of nasopharyngeal cancer (NPC) is radiation therapy (RT). The doses and volumes may differ from center to center. Most studies and guidelines recommend atotal dose of 60 Gy for elective nodal and peritumoral volume treatment. This retrospective analysis aimed to analyze whether adose reduction to 54 Gy to this volume would be associated with ahigher risk of recurrence. Atotal of 111patients treated by intensity-modulated radiotherapy (IMRT) and concurrent chemotherapy were retrospectively analyzed. The recurrent tumor volume was classified as "in field" if 95% of the recurrent volume was inside the 95% isodose, as "marginal" if 20-95% of the recurrence was inside the 95% isodose, or as "outside" if less than 20% of the recurrence was inside the 95% isodose. Median follow-up was 67months (range 6-142). The 2‑ and 5‑year overall survival (OS) rates were 88.6% and 70%, respectively. The 2‑year locoregional control (LRC), disease-free survival (DFS), and distant metastasis-free survival (DMFS) were 93.3%, 89.3%, and 87.4%, and the 5‑year LRC, DFS, and DMFS were 86.8%, 74%, and 81.1%, respectively. Ten patients (9%) had alocal and or regional recurrence. Half of the patients with locoregional failure had in-field recurrences. For primary tumor, there was no recurrence in the volume of 54 Gy. For regional lymph node volume, recurrence was detected in two (1.8%) patients in the volume of 54 Gy. These retrospective data suggest that adose reduction may be possible for intermediate-risk volumes, especially for the primary site.