LAUSR

e20642 Background: While optimal sequencing of systemic therapy in aNSCLC is critical to achieve maximal clinical benefit, it is practically challenging to study tx sequencing through clinical trials. RWD allow retrospective, observational studies to examine tx patterns and associated clinical outcomes. Methods: 1,609 aNSCLC patients who received systemic therapies at Mount Sinai hospitals were analyzed for the number of line of therapy (LOT), therapeutic modalities (chemotherapy, targeted therapy and immunotherapy), and the sequence in which treatments were given when LOT > 1. Time to tx discontinuation (TTD) was used as a surrogate clinical endpoint for outcomes. Results: 578 of the 1,609 (36%) patients received more than one LOT. 356 (22%) received tyrosine kinase inhibitors (TKIs), and 297 (16%) received immune checkpoint inhibitors (CPIs). Kaplan-Meier analysis revealed that among 297 patients who received CPIs, median TTD was longer in the 1st line setting (295 days, 95% CI 169 to 523; n=132) than when LOT > 1 (169 days, 95% CI 113 to 269; n=165), although the difference was not statistically significant (P=0.092, log-rank test). No difference of TTD on TKIs was observed between LOT = 1 and LOT > 1 (P=0.51). With respect to tx sequencing, when patients (n=94) received TKIs as the 1st LOT, 60%, 35%, and 5% of them received another TKI, chemotherapy, or a CPI-containing regimen, respectively, as the 2nd LOT. Among patients (n=370) who progressed on 1st line platinum-based chemotherapy, 52%, 32%, and 16% received another chemo regimen, a CPI-containing regimen, or a targeted therapy, respectively, as the 2nd LOT; these percentages shifted significantly toward more CPIs (24%, 66%, 10% for chemo, CPI, targeted, respectively) when only 2016-2018 data were examined. In the 2nd line setting after platinum therapy, TTD was significantly longer in the CPI group (332 days, 95% CI 169-484) compared to the chemo group (88 days, 95% CI 65-100; P<0.0001), consistent with results from pivotal clinical trials. Conclusions: As the tx algorithm of aNSCLC has been evolving rapidly, we observed diverse tx patterns in RWD. Various tx sequences may impact patient outcomes, and therefore warrant further investigation.