A prospective randomized parallel-controlled pilot trial of stereotactic body radiation therapy versus radiofrequency ablation for the management of small renal masses.

363 Background: The potential of ablative technologies as an alternative to surgery for the treatment of small renal masses (SRMs) ≤4cm is unclear. Our objective was to evaluate the feasibility and toxicity of stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) for SRMs in a prospective randomized pilot trial. Methods: Patients scheduled for renal cell carcinoma (RCC) treatment at a single academic center were approached for the pilot trial, with the aim of recruiting 24 patients. Participants were assigned 1:1 to SBRT or RFA. Imaging (CT or MRI) using a renal tumor protocol is completed at 3, 6, 9, and 12 months post-procedure. Biopsies were completed prior to the procedure and at 12 months. Multiple clinical parameters were collected. Follow-up visits will occur at 6 month intervals following the trial up to 5 years. SBRT included an initial simulation session and a single image-guided treatment session with a prescribed dose of 25 Gy. RFA was conducted by either percutaneous or laparoscopic access with 2 cycles of 8 minutes duration each upon reaching target temperature. Results: Beginning in December 2019, 24 patients were recruited and randomized (SBRT = 11; RFA = 13). Eleven had SBRT, 8 RFA, 3 have not yet had treatment, and 2 became ineligible. Median age for all patients was 67 (53,85) and 17 were male. A total of 17 patients had clear cell RCC, 6 had papillary RCC (type 1), and 1 had chromophobe RCC. All patients had T1a disease. Mean procedure length (minutes) for SBRT and RFA was 15.5±7.4 and 10.5±3.9, respectively. Two patients (both SBRT) had a 12-month biopsy showing no evidence of recurrence or metastases, while two patients (1 RFA, 1 SBRT) had a 9-month CT showing no recurrence. Data are pending for the remaining patients. An early grade 2 flare-up occurred in one SBRT patient. Conclusions: Recruitment and randomization of patients with SRMs in a SBRT vs. RFA prospective trial is feasible on a timeline that allows for regular follow-up and imaging. To date, both treatment modalities have been shown to have excellent short-term safety profiles.