Background: I+N is now standard of care for first line treatment of intermediate/poor risk mRCC patients (pts). Real world data is vital to understand drug usage, toxicity and outcomes in non-trial pts. This project describes the amount and tolerability of treatment delivered including discontinuation rates, reasons for discontinuation and outcomes from the CKCis database. Methods: Pts in CKCis, a prospective Canadian database from 15 academic centers, who received first line I+N were included. The number of doses of I+N, number of pts who received single-agent nivolumab (N) and duration of single agent N were determined. Reasons for treatment discontinuation, including the rate, type, and grade of toxicities were identified. Efficacy outcomes included time to failure (TTF – time to progression, death, or second line therapy), overall response rate (ORR) and overall survival (OS). Results: The cohort consists of 182 pts. Median age was 63 yrs, 71% had clear cell histology, 11% were on a clinical trial, the IMDC risk distribution was 5% good, 63% intermediate, 32% poor. Median follow up was 8.8 m. All 4 I+N doses were received by 30% of pts of which 78% went on to receive single-agent N. Less than 4 doses of I+N were received by 70% of pts of which 28% went on to receive single-agent N. The median time on single agent N was 5.7 m. In the entire cohort, 21% of patients discontinued therapy due to toxicity. The most common toxicity events were colitis (56% of all events), pneumonitis (19%), and hepatitis (8%). There were no toxicity-related deaths. Median OS has not been reached (22 events to date). Median TTF was 12.4 m. ORR was 32% (5% complete responses). 26% of pts received second line treatment, the most common being sunitinib in 79%. Conclusions: In this real world cohort, the majority of mRCC pts did not receive all 4 doses of I+N, contrasting with clinical trial reporting, yet many of these pts went on to receive single agent N. Discontinuation rates due to toxicity were similar to those reported in CheckMate 214. Further follow up is ongoing and efficacy outcomes analyzed on the basis of treatment quantity/duration will be presented.