Proton Therapy for Primary Renal Cell Carcinoma: The First Nationwide Retrospective Study in Japan

Background/Aim: This multi-institutional study aimed to investigate the efficacy and feasibility of proton beam therapy (PBT) for renal cell carcinoma (RCC) in Japan. Patients and Methods: The survival, local control, and toxicities in 22 RCC patients treated between 2001 and 2016 at 6 Japanese PBT institutes were analyzed. Results: The 22 patients comprised 20 men and had a median age of 67 (range=42-88) years. The total irradiation dose was 60-79.6 Gy (relative biological effectiveness). Over a median follow-up of 37 months, the 3-year overall and disease-specific survival rates were 95% and 100%, respectively, and no recurrence occurred. No patient experienced grade 3 or higher adverse events. The serum blood urea nitrogen (p=0.25) and creatinine levels (p=0.95) were not significantly affected, although the mean estimated glomerular filtration rate was reduced by 7.1±11.2 ml/min/1.73 m 2 . Conclusion: Despite the small number of patients, high-dose PBT can control RCC while maintaining their renal function with high probability, and could be and alternative curative therapy especially for inoperable patients.