276 Background: Ipilimumab and nivolumab (IPI-NIVO) and IO/vascular endothelial growth factor (VEGF) inhibitor combinations (IOVE) are now standard of care 1L treatment options for mRCC. However, there is limited head-to-head comparative evidence between these strategies. Methods: Using the IMDC dataset, patients treated with a 1L IOVE combination (pembrolizumab axitinib, avelumab axitinib and nivolumab cabozantinib) were compared with those treated with IPI-NIVO. The outcomes of interest were overall response rate (ORR), treatment duration (TD), time to next treatment (TTNT), and overall survival (OS). A preplanned subgroup analysis of the IMDC intermediate/poor risk population was conducted. Hazard ratios were adjusted for IMDC risk factors. Results: 723 patients were included for analysis (N=571 for IPI-NIVO and N=152 for IOVE). The median age was 60 in both groups. The proportion of patients with IMDC favorable, intermediate and poor risk disease in IPI-NIVO vs. IOVE groups were 9% vs. 33%, 58% vs. 53%, 33% vs. 14%, respectively. In the intermediate/poor risk groups (Table), ORR and median TD were lower and shorter in IPI-NIVO vs IOVE while no difference in median TTNT and OS was detected. The HR for death adjusting for IMDC criteria for IPI-NIVO vs. IOVE was 0.92 (95% CI 0.61-1.40, p=0.71). IMDC risk groups and the presence or absence of sarcomatoid histology, brain, liver or bone metastases were not associated with differences in OS between these treatments (all p>0.2). Patients that had dose delays or steroid use (defined as >40mg of prednisone equivalent/day) for immune related adverse events (irAEs) were associated with longer median TTNT (21.6 vs. 9.5 mons, p=0.02) and OS (NR vs. 44.4 mons, p=0.01) despite similar treatment durations (7.6 vs. 8.9 mons, p=0.77) compared to those without dose delays or steroid use. Conclusions: We were unable to detect any differences in OS between IPI-NIVO and IOVE regimens in the IMDC intermediate/poor risk groups and amongst various subgroups. Patients who experienced irAEs requiring dose delay or steroids had longer overall survival. [Table: see text]