LAUSR

e20705 Background: Based on superior outcomes noted in KEYNOTE-189 with the addition of pembrolizumab to platinum doublet chemotherapy, a majority of pts with nonsquamous NSCLC are now treated with chemoIO. irAEs can cause significant morbidity and occasionally mortality in pts treated with immunotherapy. Since chemotherapy is immunosuppressive, it is plausible that incidence of irAEs would be lower in pts receiving chemoIO compared to immunotherapy. The incidence of irAEs in KEYNOTE-189 was 22.7% vs 29.2% in KEYNOTE-024 with pembrolizumab monotherapy. We sought to evaluate the incidence and patterns of irAEs in pts with advanced nonsquamous NSCLC treated with chemoIO at our institution and to determine if the rate varied with the intensity of chemotherapy [carboplatin/ pemetrexed/ pembrolizumab (CPP) vs pemetrexed/ pembrolizumab (PP)]. Methods: We retrospectively reviewed the charts of 73 pts with advanced nonsquamous NSCLC who received CPP followed by maintenance PP. In addition to clinicopathologic variables, we noted the date, incidence, type and grade of irAEs. Descriptive statistics were used to report the incidence and patterns of irAEs. McNemar’s test was used to determine if there was a significant difference in rate of irAEs during CPP vs PP. Results: Of the 73 pts, 52% were females, 67% former smokers, 49% had previously received radiation and 11% had a history of autoimmune disease. 35 pts received 4 cycles of CPP. 21 patients (28%) developed irAEs, of which 6 had irAEs during CPP and 15 developed irAEs on PP. The rate of irAEs was significantly higher after stopping carboplatin (p = 0.049). 10 pts (13%) stopped pembrolizumab due to irAEs. Organ systems involved and grade of irAEs are listed below. Conclusions: The immunosuppressive effects of intensive chemotherapy may be protective against irAEs in pts receiving chemoIO. [Table: see text]