Re-irradiation with Moderate Hypo-fractionation Using Intensity Modulated Photon or Proton Radiation Therapy in Locally Recurrent Squamous Cell Carcinoma of Nasopharynx

Purpose This study aimed to analyze the treatment outcomes of locally recurrent nasopharyngeal cancer (NPC) patients following moderate hypo-fractionation re-irradiation (re-RT). Materials and Methods Sixty locally recurrent NPC patients underwent hypo-fractionation re-RT. Forty-eight point three percentage had rT3-4, and 30.0% did keratinizing squamous cell carcinoma. Intensity-modulated radiation therapy (IMRT), with or without intensity-modulated proton therapy (IMPT), was used in 66.7% of patients. Results With the median follow-up of 22 months (range, 2 to 254 months), 31 patients (51.7%) died, 38 (63.3%) developed further treatment failure, and 30 (50.0%) developed ≥ grade 3 toxicity (including seven grade 5) at time of analysis. The 2- and 5-year rates of overall survival, local failure-free survival, and ≥ grade 3 toxicity-free survival were 57.9% and 45.8%, 64.1% and 52.5%, and 54.8% and 44.9%, respectively. In multivariate analyses, worse factors for overall survival (OS) were iT3-4 (p=0.010) and age at re-RT ≥ 53 years (p=0.003), those for local failure-free survival (LFFS) were rT3-4 (p=0.022) and rN0-1 (p=0.035), and those for toxicity-free survival (TFS) were iT3-4 (p=0.020) and re-IMRT/IMPT (p=0.030), respectively. Cumulative dose or fraction size ≥ 3 Gy at re-RT, however, showed no significance for OS, LFFS and TFS. Conclusion Current re-RT with modern RT techniques by moderate hypo-fractionation scheme seemed feasible in treating locally recurrent NPC patients.