Background: Randomized data from the interferon era demonstrated modest survival benefits of cytoreductive nephrectomy (CN) in patients with advanced renal cell carcinoma (aRCC). Results from SURTIME and CARMENA, conducted in the VEGF-targeted therapy era, have challenged the routine use of upfront CN especially in IMDC intermediate and poor risk patients. Furthermore, the treatment landscape in aRCC now includes first-line combination immunotherapy. Data from the Checkmate-214 trial showed that intermediate/poor risk patients have improved overall survival and objective response rate with ipilimumab and nivolumab (I/N) compared to sunitinib. Stereotactic body radiation therapy (SBRT) provides a convenient method for cytoreduction of the primary kidney lesion and may induce an ‘abscopal effect’, leading to enhanced systemic anti-tumour immune response. We hypothesize that SBRT to the primary kidney mass in aRCC patients will enhance the efficacy of I/N compared to standard of care I/N alone. Methods: This phase II trial randomizes untreated aRCC patients in a 2:1 fashion to I/N plus SBRT (30-40 Gy in 5 fractions) to the primary kidney mass between cycles 1 and 2 (experimental arm, E), versus standard of care I/N alone (standard arm, S). Eligible patients have biopsy-proven aRCC (any histology), IMDC intermediate/poor risk disease, and who decline or are unsuitable for CN. Patients with a primary kidney lesion ≥ 20cm, previous abdominal radiation precluding SBRT, or who have a contraindication to I/N are excluded. The primary objective is to compare the efficacy of I/N plus SBRT versus I/N alone, as determined by the hazard ratio for progression free survival (PFS). Secondary objectives include evaluation of safety, overall survival, objective response rate, and health-related quality of life. Exploratory analyses include blood immune signatures and stool microbiome. Up to 78 patients will be enrolled under the assumption of an improved 12-month PFS from 50% (S) to 75% (E), using a two-sided α=0.1, power=80%, and accounting for loss-to-follow-up and stratification using IMDC criteria 1-2 vs 3-6. Clinical trial information: NCT04090710.