Is fractionated robotic stereotactic body radiosurgery optional salvage treatment for the re-irradiation of locally recurrent nasopharyngeal carcinoma?

Recurrent nasopharyngeal carcinoma (NPC) after previous radiation therapy is a significant problem. This study was to determine the potential benefits from re-irradiation by fractionated stereotactic body radiotherapy (FSRT) on survival benefits and effects of severe late toxicities.Between 2009 and 2018, treatment outcomes were evaluated retrospectively in 26 patients with locally recurrent NPC treated using FSRT with CyberKnife. Five patients who had metastatic disease and one who had second recurrence were excluded from the study, and the remaining 20 patients were analyzed. The median age was 52 years (range, 28-80 years); re-treatment T stage was as follows: 6 (30%) - T2, 5 (25%) - T3, and 9 (45%) - T4. The median time from initial RT to recurrence was 22 months (range, 8-159 months). The median re-irradiation FSRT dose was 30 Gy in 5 fractions.The median follow-up was 44 months; the overall survival (OS), local failure-free survival, and disease progression-free survival rates at 3 years were 89%, 73%, and 53%, respectively. All patients were evaluated for response after treatment: 9 (45%) had complete, 3 (15%) had partial, and 6 (30%) had no response. Univariate analysis demonstrated that higher cumulative total radiotherapy dose, gross tumor volume, and recurrent time interval were prognostic factors for local failure-free survival. The recurrent time interval was also an independent factor for progression-free survival and OS. The incidence of temporal lobe necrosis and trismus was 10% and 20%, respectively. One patient had Grade 5 toxicity to treatment-related bleeding.Tumor dose coverage is important for treating recurrent NPC, and treatment-related mortality was vascular in nature. FSRT is a promising treatment modality for recurrent NPC.