545P Completion of pembrolizumab in advanced non-small cell lung cancer: Real-world outcomes after two years of therapy (COPILOT)

Immune checkpoint inhibitors (ICI) are standard of care in advanced non-small cell lung cancer (NSCLC) without driver mutations. A small proportion of patients (pts) treated with ICIs will achieve durable responses. We describe outcomes of a real-world cohort of pts who completed two years of pembrolizumab (pembro). Clinical data of pts who completed 35 cycles of first-line pembro for NSCLC (or 30-34 cycles with reason for cessation other than progression) was collected retrospectively from sites across Australia via the AUstralian Registry and biObank of thoRacic cAncers (AURORA). Primary endpoints were progression rate post pembro completion and progression free survival (PFS). Local treatment of oligoprogressive disease during pembro was included. Analyses were performed using R. 71 pts from six centres with a median age of 66.0 yrs, 49% male & 90% ECOG≤1 were identified. Pts were Caucasian (82%) or Asian (16%); past (69%) or current (25%) smokers with a mean 37 pack year history. Histology comprised 73% adenocarcinoma, 16% squamous. 18 pts (25%) had brain mets at diagnosis, 16 treated (8 resected, 8 RT). Median PD-L1 tumour proportion score (TPS) was 68%; 12 pts (17%) PD-L1 negative, 43 pts (61%) TPS≥50%. No pts had ALK/ROS/EGFR mutations; 29/49 tested (60%) had K-Ras mutations. Median follow up from pembro start was 38.7 months (24.5 – 65.6).Table: 545PTotal population (n=71)Pembro39 (55%)Median time on pembro24.2 moPembro + chemo32 (45%)(20.0-35.3)Objective Response Rate (ORR)78.6%76.9%CR20 (29%)ORR pembro80.6%PR35 (50%)ORR pembro+chemop=0.86Median PFS46.1 mo (95%CI 39.5-NR)PFS in PD-L1≥1%PFS in PD-L1 negNR (46.1-NR)28.1 mo (16.3-NR)p=0.013Oligoprogression during pembroTotal17 (24%)Locoregional8PFS oligo subgroup12.0 mo (9.4-18.9)Brain7PFS223.1 mo (20.2-NR)Progression post pembroTotal20 (28%)Median time to progression3.3 mo (1.0-26.3)Locoregional11Brain3Bone5PD-L1≥1%13Pts with CR2PD-L1 neg6 (OR 3.46, p=0.06)Pts without CR18 (OR 5.06, p=0.04)Brain mets at diagnosis (n=18)CNS progression6 (33%) Open table in a new tab Pts completing two years of pembro for NSCLC in Australia had high rates of K-Ras mutation and PD-L1 expression; a significant proportion had brain metastases and treated oligoprogression. Progression rate post pembro was higher in PD-L1-negative pts and in those without complete response.