Abstract
BACKGROUND: Background: It is estimated that a significant number of patients presenting with metastatic RCC are either ineligible, not recommended for, or refuse surgery. There remains no well-established method for addressing the primary tumor in such patients. Stereotactic ablative radiotherapy (SABR) is a highly effective modality for the treatment of the primary tumor in RCC. Our study seeks to evaluate SABR as an alternative approach to treat the primary tumor in patients with metastatic RCC receiving immunotherapy, who are not recommended for surgery, or who decline surgery. The primary objective of the study is to determine whether the addition of SABR to the primary tumor in combination with immunotherapy improves outcomes compared to immunotherapy alone in patients with metastatic, unresected, renal cell carcinoma (RCC). The primary endpoint is nephrectomy and radiographic progression-free survival (nrPFS) with progression determined as per iRECIST criteria. Patients are eligible if they are not recommended for upfront surgery, have a primary tumor treatable with SABR, and are candidates for immunotherapy. Immunotherapy is physician’s choice and will include either two different immunotherapy regimens (IO-IO) or immunotherapy in combination with a VEGF inhibitor (IO-VEGF). METHODS: 240 patients will be randomized in a 2:1 ratio favoring SABR plus immunotherapy (n=160) as compared to standard of care immunotherapy alone (n=80). The sample size will provide 90% power at a one-sided alpha level of 0.05 to detect a hazard ratio for nrPFS of 0.61, i.e., a 40% reduction in the rate of events. One-year PFS in the nivolumab plus ipilmumab arm was 50% (n=550, intermediate/poor risk population). Checkmate 9ER (Choueiri 2021) showed a one-year PFS rate in patients receiving nivolumab plus Cabozantinib (n=323) of 45-58% (intermediate/poor risk population). We have therefore estimated a one-year nrPFS rate of 50% in the control (immunotherapy alone) arm for SAMURAI. We expect nephrectomies to contribute only a small fraction to the total nrPRS events. To detect a hazard ratio of 0.62, which corresponds under exponential distribution assumptions to an absolute 15% improvement in one-year nrPFS from 50% in the control group to 65% in the experimental arm (SABR plus immunotherapy), a total sample size of 240 patients will be enrolled. This design will provide 90% power, based on a one-sided logrank test at the 0.05 alpha level, with three years of accrual and two further years of follow-up. The expected number of nrPFS events is E=175. The calculations allow for a 10% non-eligible/early dropout rate. The trial is currently open and accruing through the NRG oncology cooperative group (NCT05327686).