A prospective, randomized, parallel-controlled pilot trial of stereotactic body radiation therapy vs. radiofrequency ablation for the management of small renal masses
Raees Cassim1, Anand Swaminath2, Jen Hoogenes1, Oleg Mironov3, Braden Millan1, Edward D. Matsumoto1, Anil Kapoor1.
1Department of Surgery, Division of Urology, McMaster University, Hamilton, ON, Canada; 2Department of Oncology, Faculty of Health Sciences, McMaster University, Hamilton, ON, Canada; 3Department of Radiology, Faculty of Health Sciences, McMaster University, Hamilton, ON, Canada
Introduction: The potential of ablative technologies in replacing surgery for the treatment of small renal masses (SRMs) ≤4 cm is unclear. Our objective was to evaluate the feasibility and toxicity of stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) for SRMs to determine the utility of a future full-scale multicenter trial.
Methods: Patients scheduled for SRM treatment at a single academic center were approached for this pilot trial, with the aim of recruiting 24 patients. Participants were randomized to SBRT or RFA. Imaging (computed tomography or magnetic resonance imaging) is completed at three, six, nine, and 12 months post-procedure. Crossover, if ineligible for treatment after randomization, was allowed. Biopsies were completed prior to the procedure and at 12 months. 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 two cycles of eight minutes duration each upon reaching target temperature.
Results: Twenty-four patients were recruited and randomized over 18 months (SBRT=11; RFA=13). Fourteen had SBRT, eight RFA, and two became ineligible. The median age for all patients was 67 years (53,85) and 17 were male. Seventeen patients had clear-cell renal cell carcinoma (RCC), six had papillary RCC, and one 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 of five patients (four SBRT, one RFA) who had a 12-month biopsy demonstrated viable tumor (two SBRT). An additional five patients (one RFA, four SBRT) had nine-month imaging demonstrating no tumor growth. Additional data are not yet available for the remaining patients. An early grade 2 flareup occurred in one SBRT patient.
Conclusions: Recruitment and randomization of patients with SRMs is feasible on a timeline that allows for regular followups and imaging. Thus far, both treatments have been shown to have an excellent short-term safety profile.
