Background: Immuno-oncology (IO) checkpoint inhibitor treatment outcomes are poorly characterized in the real world metastatic renal cell cancer (mRCC) patient population, including geriatric patients. Methods: Using the IMDC database, a retrospective analysis was performed on mRCC patients treated with IO, as listed below. Patients received one or more lines of IO therapy, with or without a targeted agent. Duration of treatment (DOT) and overall response rates (ORR) were calculated. Cox regression analysis was performed to examine the association between age as a continuous variable and DOT. Results: 312 mRCC patients treated with IO were included. In patients who were evaluable, ORR to IO therapy was 29% (32% first-, 22% second-, 33% third-, and 32% fourth-line treatment (Tx)). Patients treated with second-line IO therapy were divided into favorable, intermediate, and poor risk using IMDC criteria; the corresponding median DOT rates were not reached (NR), 8.6 mo, and 1.9 mo, respectively (p<0.0001). Based upon age, hazard ratios were calculated in the first- through fourth-line therapy setting, ranging from 1.03 to 0.97. Conclusions: The ORR to IO appears to remain consistent, regardless of line of therapy. In the second-line, IMDC criteria appear to appropriately stratify patients into favorable, intermediate, and poor risk groups for DOT. Premature OS data will be updated. In contrast to clinical trial data, longer DOT is observed in real world practice. Age may not be a factor influencing DOT.