Phase II trial of stereotactic ablative radiation (SAbR) for oligoprogressive kidney cancer.

Abstract

4564 Background: Metastatic renal cell carcinoma (mRCC) patients on systemic therapy may experience oligoprogression. SAbR has been demonstrated to be safe and is associated with high local control rates in mRCC. In this prospective phase II single arm trial, we investigated SAbR to control oligoprogressive mRCC. Methods: Patients with mRCC who demonstrated response to systemic therapy with subsequent radiographic evidence of three or fewer sites of progression were treated with SAbR to all progressive sites. Systemic therapy was held during SAbR at the discretion of the treating oncologist. Follow-up included radiographic imaging at three-month intervals. Sequential SAbR for continued oligoprogression was allowed. The primary objective was extension of ongoing systemic therapy by >6 months in 40% of the patients. Progression was defined by any of these 3 criteria: (1) local failure at a radiated site; (2) progression ineligible for additional SAbR (>3 sites) or involving >30% of metastasis; or (3) progression as clinically determined by treating physicians. An exact binomial test was used to test the probability of postponing systemic therapy. Secondary endpoints focused on overall survival (OS), local control (LC) rates, toxicity, and health-related quality of life (QOL). Results: The trial completed accrual with enrollment of 20 patients who received SAbR to a total of 36 sites. At enrollment four, twelve, three, and one patients were on first, second, third, and fourth line of systemic therapy, respectively. Eleven were on immunotherapy and nine on a tyrosine-kinase inhibitor. Three patients required repeat SAbR to a new site for sequential disease control. At a median follow-up of 8.3 months (interquartile range 3.9 – 15.1), SAbR extended the duration of the ongoing systemic therapy by >6 months in 12 out of 17 patients (70.6%, 95% CI: 48.9%-92.3%). Thirteen out of 20 patients progressed with a median PFS of 8.7 months (95% CI: 3.2-12.4). Five patients died and the OS did not reach the median. LC was 36/36 (100%). Treatment related grade 1 and grade 2 toxicity was experienced by three and one patient, respectively; no grade 3 toxicities were reported. When compared to baseline, no significant decline in QOL was detected. Conclusions: SAbR extended PFS of ongoing systemic by >6 months in oligoprogressive patients with mRCC. SAbR was safe and did not adversely affect QOL. These data support further evaluation of SAbR for oligoproressive mRCC in a prospective randomized setting. Clinical trial information: NCT03696277.