Proton pencil-beam scanning radiotherapy in the treatment of nasopharyngeal cancer: dosimetric parameters and 2-year results.

Objectives:  Patients with nasopharyngeal cancer are candidates for proton radiotherapy due to large and comprehensive target volumes, and the necessity for sparing of healthy tissues. The aim of this work is to evaluate treatment outcome and toxicity profile of patients treated with proton pencil-beam scanning radiotherapy.

Materials And Methods:  Between Jan 2013 and June 2018, 40 patients were treated for nasopharyngeal cancer (NPC) with IMPT (proton radiotherapy with modulated intensity). Median age was 47 years and the majority of patients had locally advanced tumors (stage 2-8 patients. (20%); stage 3-18 patients (45%); stage 4A-10 patients. (25%); stage 4B-4 patients. (10%). Median of total dose was 74 GyE (70-76 GyE) in 37 fractions (35-38). Bilateral neck irradiation was used in all cases. Concomitant chemotherapy was applied in 34 cases. (85%). Median follow-up time was 24 (1.5-62) months.

Results: Two-year overall survival (OS), disease-free survival (DFS), and local control (LC) were 80%, 75%, and 84%, respectively. Acute toxicity was generally mild despite large target volumes and concurrent application of chemotherapy with skin toxicity and dysphagia reported as the most frequent acute side effects. The insertion of a percutaneous endoscopic gastrectomy (PEG) was necessary in four cases (10%). Serious late toxicity (G > 3. RTOG) was observed in two patients (5%) (dysphagia and brain necrosis).

Conclusion:  IMPT for nasopharyngeal cancer patients is feasible with mild acute toxicity. Treatment outcomes are promising despite the high percentage of advanced disease in this group.