Background: Immunotherapy-based combination therapies (IO-X) are standard of care for metastatic RCC (mRCC) in the frontline setting. Limited data is available on the role of cytoreductive nephrectomy prior to IO-X in patients (pts) with mRCC (Bakouny, et al. GU ASCO 2020). We assessed the correlation between nephrectomy prior to IO-X and overall survival (OS) in pts with de novo mRCC. Methods: We pooled data from trials submitted for FDA review of a checkpoint inhibitor combination as first-line treatment for pts with mRCC. We only included trials with available data for stage at initial diagnosis (dx) to identify pts with stage IV disease at initial dx and to exclude those with nephrectomy in the non-metastatic setting. Kaplan-Meier method was used to estimate median OS in pts with de novo mRCC with and without nephrectomy prior to IO-X. Results: Five trials met inclusion criteria, all of which evaluated IO in combination with a kinase inhibitor. Data for stage at initial dx was available in 1708 pts who received IO-X. The majority of pts were male (72%) and White (80%). Among the 849 pts (50%) with stage IV RCC at initial dx, 523 pts (62%) had nephrectomy prior to IO-X. All pts had clear cell histology; Sarcomatoid differentiation was present in tumor pathology of 25% and 10% of pts with and without prior nephrectomy, respectively. Proportion of pts with favorable, intermediate and poor risk disease was 10%, 70% and 20%, respectively. OS appeared better in those with stage IV disease at dx who had prior nephrectomy compared to pts without nephrectomy (Hazard ratio (HR) = 0.53, 95% CI: 0.42, 0.68), even after adjusting for age and prognostic risk group (HR = 0.59, 95% CI: 0.46, 0.75) (see table). Conclusions: In this retrospective exploratory analysis, nephrectomy prior to IO-X in pts with new dx of stage IV RCC appeared to be associated with improved OS, even when controlling for age and prognostic risk group. The decision for nephrectomy is affected by factors such as medical comorbidities which could not be completely controlled. Results should be considered hypothesis generating.