A Japanese registry study and systematic review of particle therapy for renal cell carcinoma.

The feasibility and efficacy of particle beam therapy (PBT) using protons or carbon ions were compared with those of photon-based stereotactic body radiotherapy (SBRT) for primary renal cell carcinoma (RCC) via a systematic review and nationwide registry for PBT (Japanese Society for Radiation Oncology [JASTRO] particle therapy committee). Between July 2016 and May 2019, 20 patients with non-metastatic RCC who were treated at six Japanese institutes (using protons at three, using carbon ions at the other three) were registered in the nationwide database and followed up prospectively. The 20 patients comprised 15 men and had a median age of 67 (range: 57-88) years. The total radiation dose was 66-79.6 Gy (relative biological effectiveness [RBE]). Over a median follow up of 31 months, the 3-year rates of overall survival (OS) and local control (LC) were 100% and 94.4%, respectively. No grade ≥ 3 toxicities were observed. Based on a random effects model, a meta-analysis including the present results revealed 3-year OS rates after SBRT and PBT of 75.3% (95% CI: 57.3-86.6) and 94.3% (95% CI: 86.8-97.6), respectively (P = 0.005), but the difference in LC rates between the two methods was not observed (P = 0.63). PBT is expected to have similar if not better treatment results compared with SBRT for primary renal cancer. In particular, PBT was shown to be effective even for large RCC and could provide a therapeutic option when SBRT is not indicated.