141O Durvalumab (D) ± tremelimumab (T) + platinum-etoposide (EP) in 1L extensive-stage (ES) SCLC: Characteristics of long-term survivors in the CASPIAN study

In the phase 3 CASPIAN trial, 1L D+EP significantly improved OS vs EP and benefit was sustained after >3 years median follow-up (HR 0.71; 95% CI 0.60‒0.86; nominal p=0.0003). Here we assess clinical molecular characteristics of pts who experienced long-term survival in CASPIAN. 805 with ES-SCLC were randomised 1:1:1 to D+EP, D+T+EP or EP. post-hoc analyses, assessed survivors (LTS; n=94), defined as still alive at 22 Mar 2021 data cutoff (DCO; 39.4 mo). PD-L1 expression tissue tumour mutational burden (tTMB) biomarker evaluable populations (BEPs) according landmark (18 36 There 44 (16%), 37 (14%) 13 (5%) LTS arms, respectively. had slightly higher incidence some favourable prognostic factors baseline; brain/liver mets lower among ITT, although they occurred (Table). More received ≥4 cycles than a overall treatment exposure IO+EP arms. 46 (27 D+EP; 19 D+T+EP) ongoing D this DCO. ORR 24-mo PFS rates for ITT Rates serious AEs (SAEs) similar arm only, on ≥1% cells (TC) immune (IC) (but not tTMB >10 mut/Mb) enriched ≥18 mo <18 (Table); enrichment maintained ≥36 (data will be presented). times many arm. more likely have baseline. Notably, most completed induction and, both substantially greater exposure, well achieving longer PFS, ITT. no evidence cumulative toxicity based SAEs.Table: 141OD+EPD+T+EPEPLTSITTLTSITTLTSITTn442683726813269Median age, yrs59.56259636363Male, %507170755468PS 0, %433746413133Brain mets, %710814010Liver %204030441539Median wks15928160232019D dose delays, %75577659‒‒≥4 EP, %*1008792819285Unconfirmed ORR, %†89799274697124-mo %†65116712553SAEs, %343254473136BEP, n/N (%)OS moOS moPD-L1 (TC IC) ≥1%13/46 (28)25/106 (24)24/47 (51)30/110 (27)7/24 (29)25/103 (24)tTMB mut/Mb16/29 (55)41/78 (53)16/30 (53)32/75 (43)4/16 (25)22/55 (40)*Based etoposide†From 27 Jan 2020 DCO; RECIST collected DCO Open table new tab