Abstract

LBA5 Background: The standard of care (SoC) for pts with LS-SCLC is concurrent platinum-based chemoradiotherapy (cCRT) ± prophylactic cranial irradiation (PCI). ADRIATIC (NCT03703297), a phase 3, randomized, double-blind, placebo (PBO)-controlled, multicenter, global study, assessed D ± tremelimumab (T) as consolidation tx for pts with LS-SCLC who had not progressed after cCRT. Here we report results for D vs PBO from the first planned interim analysis (IA). Methods: Eligible pts had stage I–III LS-SCLC (stage I/II inoperable) and WHO performance status 0/1, and had not progressed after cCRT. PCI was permitted before randomization. Pts were randomized 1–42 days after cCRT to D 1500 mg + PBO, D 1500 mg + T 75 mg, or PBO + PBO every 4 weeks (Q4W) for 4 cycles, followed by D (D±T arms) or PBO Q4W until investigator-determined progression or intolerable toxicity, or for a maximum of 24 months (mo). The first 600 pts were randomized in a 1:1:1 ratio; subsequent pts were randomly assigned 1:1 to D or PBO. Randomization was stratified by stage (I/II vs III) and receipt of PCI (yes vs no). The dual primary endpoints were OS and PFS (blinded independent central review per RECIST v1.1) for D vs PBO. OS and PFS for D+T vs PBO were alpha-controlled secondary endpoints. Results: 730 pts were randomized, including 264 to D and 266 to PBO. Baseline characteristics and prior tx were well balanced between arms. Radiation schedule in the D vs PBO arms was once daily in 73.9% vs 70.3% of pts and twice daily in 26.1% vs 29.7%; 53.8% of pts in each arm received PCI. At this IA (data cutoff 15Jan2024), median (range) duration of follow-up for OS and PFS in censored pts was 37.2 (0.1–60.9) and 27.6 (0.0–55.8) mo, respectively. OS was significantly improved with D vs PBO (HR 0.73 [95% CI 0.57–0.93]; p=0.0104; median OS 55.9 [95% CI 37.3 – not estimable] vs 33.4 [25.5–39.9] mo; 24-mo OS rate 68.0% vs 58.5%; 36-mo OS rate 56.5% vs 47.6%). PFS was also significantly improved with D vs PBO (HR 0.76 [95% CI 0.61–0.95]; p=0.0161; median PFS 16.6 [95% CI 10.2–28.2] vs 9.2 [7.4–12.9] mo; 18-mo PFS rate 48.8% vs 36.1%; 24-mo PFS rate 46.2% vs 34.2%). Tx benefit was generally consistent across predefined pt subgroups for both OS and PFS. With D vs PBO, maximum grade 3/4 all-cause adverse events (AEs) occurred in 24.3% vs 24.2% of pts; AEs led to tx discontinuation in 16.3% vs 10.6% of pts and to death in 2.7% vs 1.9%. Any-grade pneumonitis/radiation pneumonitis was reported in 38.0% vs 30.2% of pts with D vs PBO (maximum grade 3/4 in 3.0% vs 2.6%). The D+T arm remains blinded until the next planned analysis. Conclusions: D as consolidation tx after cCRT demonstrated a statistically significant and clinically meaningful improvement in OS and PFS compared with PBO in pts with LS-SCLC. D was well tolerated and AEs were consistent with the known safety profile, with no new signals observed. These data support consolidation D as a new SoC for pts with LS-SCLC who have not progressed after cCRT. Clinical trial information: NCT03703297 .