91P Observational retro-prospective study on immune checkpoint inhibitors (ICIs) treatment duration in patients with advanced non-small cell lung cancer (aNSCLC) (I-STOP study)

Data on optimal ICI treatment duration in aNSCLC are scarce, especially in real-world (RW) settings. I-STOP is an ongoing observational, multicentre, retro-prospective study looking at aNSCLC patients (pts) treated with single-agent ICI for at least 24 months in 17 Italian centres. Cohort 1 (C1) encompassed pts who continued treatment after 24 months by clinical choice, and Cohort 2 (C2) included pts who stopped treatment at 24 months. One loco-regional procedure for oligo-progressive disease (PD) was allowed. The study aims to assess safety and effectiveness in both cohorts. As of December 20, 2023, 100 pts were enrolled. Most received ICI as 1st line (60%); notably, 37 received radiotherapy for oligo-PD, 36 had ECOG PS ≥2, and 19 had stable disease (SD) as the best response. Seventy-three pts continued ICI after 24 months (C1), and 27 discontinued treatment (C2) (Table). After a median follow-up of 48.5 months (40.0-62.7) from ICI initiation, reported immune-related adverse events (irAEs) were: 41% (30 pts) and 37.5% (9 pts) in C1 and C2 respectively, with thyroid dysfunction being the most common. No grade 3-4 events were reported after the 24-month treatment, and no patient discontinued treatment due to irAEs in C1 after 24 months. Median Progression-Free Survival (mPFS) and Overall Survival (mOS) were not reached in both cohorts; 16 patients (21.9%) had PD in C1, while 5 (20.8%) in C2. Two pts (2.7%) died to PD in C1, 0 in C2. Two pts (8.3%) with PD in C2 underwent ICI rechallenge and are still on treatment. Table: 91PBaseline characteristicsCohort 1 (n=73)Cohort 2 (n=27)Median age at diagnosis, year67.7 (59.6-70.5)65.3 (59.1-72.4)Female n (%)23 (31)16 (59)Histology n (%)Adenocarcinoma60 (82)23 (85)Squamous carcinoma12 (16)4 (15)UNK1 (1)0PD-L1 n (%)>50%38 (52)23 (85)1-49%9 (12)1 (4)<1%9 (12)2 (7)UNK17 (23)1 (4)ICI employed n (%)Nivolumab16 (22)1 (4)Atezolizumab20 (27)3 (11)Pembrolizumab37 (51)23 (85)Lines of therapy n (%)137 (51)23 (85)≥ 236 (49)4 (15) Open table in a new tab In this RW population, ICI demonstrated effectiveness beyond 24 months, with low rates of PD even in patients who discontinued treatment at fixed time point (24 month). Enrolment and follow-up are ongoing to better assess differences between the two cohorts.