Objectives: First-line pemetrexed-platinum chemotherapy + osimertinib(Pem-Plat-Osi) improves progression-free survival as compared to osimertinib alone in advanced epidermal growth factor (EGFR)-mutated non-small cell lung cancer (NSCLC). However, many patients are hesitant to commence chemotherapy upfront. We describe outcomes to Pem-Plat-Osi after first-line osimertinib failure., Materials and Methods: Patients with advanced EGFR-mutated (ex19del/L858R) NSCLC who had Pem-Plat-Osi between 1/7/2018-30/9/2023 after progression on first-line osimertinib at National Cancer Centre Singapore, Prince of Wales Hospital and Chinese University of Hong Kong were identified. Key endpoints were time to treatment failure (TTF) and overall survival (OS)., Results: A total of 60 patients were included. Median age at diagnosis was 62, 53.3 % (32/60) were male and 76.7 % (46/60) were never smokers. Ex19del comprised 56.7 % (34/60) and L858R 43.3 % (26/60). Baseline central nervous system (CNS) metastases were present in 66.7 % (40/60). Median TTF on osimertinib (TTF1) was 14.4 months(m) and median time to initiation of Pem-Plat-Osi was 41 days(d) (range 0-652) after progression on osimertinib. Partial response (PR) or stable disease to Pem-Plat-Osi was achieved in 81.7 %(49/60). Intracranial disease control was achieved in 90.6 % (29/32) of patients with measurable CNS metastases, including those who did not undergo brain radiotherapy. At median follow up of 31.2 m, median TTF on Pem-Plat-Osi (TTF2) was 6.6 m. Median TTF1 + TTF2 was 23.4 m and median OS was 34.2 m. Survival outcomes were similar comparing ex19del and L858R (median TTF1 + TTF2 21.8 m vs 23.5 m, p = 0.90; median OS 34.2 m vs 36.8 m, p = 0.37) and in patients without/with baseline CNS metastases (median TTF1 + TTF2 21.8 m vs 23.4 m, p = 0.44; median OS 36.2 m vs 31.9 m, p = 0.65). TTF1 duration was not significantly associated with TTF2 (p = 0.76). Patients who started Pem-Plat-Osi within 20d of progression on osimertinib had significantly longer TTF2 as compared to patients who started after 20d (median 8.4 m versus 6.0 months, p = 0.03), which remained statistically significant on multivariable analysis., Conclusions: Our real-world data supports the efficacy of Pem-Plat-Osi after progression on first-line osimertinib, including L858R and baseline CNS metastases. Chemotherapy initiation within 20d of Osi progression was predictive of superior TTF2., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Dr Saw reports grants from Astra Zeneca, consulting fees from Pfizer, Bayer, Astra Zeneca and Daiichi Sankyo, honoraria from Astra Zeneca, MSD, Bristol-Myers Squibb, Daiichi Sankyo, Roche and Takeda, meeting support from MSD and Astra Zeneca from Pfizer, advisory board participation from Astra Zeneca, Daiichi Sankyo and Pfizer, outside the submitted work. Dr Lai reports grants from Astra Zeneca, Roche and Amgen and meeting support from Astra Zeneca, outside the submitted work. Dr Chan reports meeting support from Roche, Astra Zeneca and Ipsen, outside the submitted work. Dr W.C. Tan reports grants from Singhealth, honoraria from Merck & Co, MSD and Astra Zeneca, meeting support from Ipsen Pharmaceuticals and Merck & Co, outside the submitted work. Dr A. Tan reports consulting fees from Amgen, Bayer and Pfizer, honoraria from Amgen, Guardant Health, Takeda, Juniper Biologics and Astra Zeneca, outside the submitted work. Dr W.L. Tan reports grants from Astra Zeneca, honoraria from Novartis and Merck, meeting support from Astra Zeneca, MSD, Boehringer Ingelheim and Ipsen, outside the submitted work. Dr Kanesvaran reports honoraria from Astellas, MSD and Ipsen, leadership roles in ESMO and SIOG, outside the submitted work. Dr Lim reports grants from Taiho Pharmaceuticals, consulting fees from Daiichi Sankyo, Amgen, Janssen and Alentis Therapeutics, honoraria from MSD and Takeda, meeting support from Astra Zeneca and Alentis Therapeutics, outside the submitted work. Dr. Tan reports grants from ACM Biolabs, Amgen, Astra Zeneca, Bayer and Pfizer, consulting fees from Amgen, Astra Zeneca, Bayer, Boehringer Ingelheim, DKSH, GlaxoSmithKline, Merck, Novartis, Pfizer, Roche and Takeda, honoraria from Amgen, Bayer, Merck, Pfizer, Novartis, Boehringer Ingelheim, Roche, Takeda, Beigene, Regeneron, Zymeworks, meeting support from Bayer, Merck, Pfizer, Regeneron and Zymeworks, outside the submitted work. Dr Mok reportsgrantsfrom AstraZeneca, Bristol Myers Squibb, G1 Therapeutics, Merck Sharp & Dohme, Merck Serono, Novartis, Pfizer, Roche, SFJ, Takeda, XCovery, consulting fees from Abbvie Inc, ACEA Pharma, Adagene, Alentis Therapeutics AG, Alpha Biopharma Co., Ltd, Amgen, Amoy Diagnostics Co,AnHeart Therapeutics Inc,AVEO Pharmaceuticals, Inc,Bayer Healthcare Pharmaceuticals Ltd,BeiGene,BerGenBio ASA,Berry Oncology,Boehringer Ingelheim,Blueprint Medicines Corporation,Bristol Myers Squibb,Bowtie Life Insurance Company Limited,Bridge Biotherapeutics Inc,Covidien LP,C4 Therapeutics Inc,Cirina Ltd,CStone Pharmaceuticals,Curio Science,D3 Bio Ltd,Da Volterra,Daiichi Sankyo,Eisai,Elevation Oncology,F. Hoffmann-La Roche Ltd./ Genentech,Fishawack Facilitate Ltd,G1 Therapeutics Inc,geneDecode Co., Ltd,Gilead Sciences, Inc,GLG’s Healthcare,Gritstone Oncology, Inc,Guardant Health,Hengrui Therapeutics Inc,HiberCell, Inc.,HutchMed,Ignyta Inc.,Illumina Inc.,IncyteCorporation,Inivata,IQVIA,Janssen,Lakeshore Biotech Ltd,Lilly,Lunit USA, Inc,Loxo-Oncology,Lucence Health Inc,Medscape LLC/ WebMD,Medtronic,Merck Serono,MSD,Mirati Therapeutics Inc,MiRXES,MoreHealth,Novartis,Novocure GmbH,Omega Therapeutics Inc,OrigiMed,OSE Immunotherapeutics,PeerVoice,Pfizer,PrIME Oncology,Prenetics Global Limited,Puma Biotechnology Inc,Qiming Development (HK) Ltd,Regen Medtech Holdings Limited,Regeneron Pharmaceuticals Inc.,Roche Pharmaceuticals/ Diagnostics/ Foundation One,Sanofi-Aventis,SFJ Pharmaceutical Ltd,Simcere of America Inc,Synergy Research,Summit Therapeutics Sub, Inc,Takeda Pharmaceuticals HK Ltd,Tigermed,Vertex Pharmaceuticals,Virtus Medical Group,XENCOR, Inc,Yuhan Corporation,honorariafromACEA Pharma,Alpha Biopharma Co.Ltd,Amgen,Amoy Diagnostics Co. Ltd,AstraZeneca (before 1/1/19),BeiGene,BI,BMS,Daiichi Sankyo,Daz Group,Fishawack Facilitate Ltd.,InMed Medical Communication,Janssen Pharmaceutica NV,Jiahui Holdings Co. Limited,LiangYiHui Healthcare,Lilly,Lucence Health Inc.,MD Health Brazil,Medscape LLC,Merck Pharmaceuticals HK Ltd.,Merck Sharp & Dohme,MiRXES,Novartis,OrigiMed Co. Ltd.,P. Permanyer SL,PeerVoice, Physicians’ Education Resource,Pfizer,PrIME Oncology,Research to Practice,Roche Pharmaceuticals/ Diagnostics/ Foundation One,Sanofi-Aventis,Shanghai BeBirds Translation & Consulting Co. Ltd,Taiho Pharmaceutical Co. Ltd,Takeda Oncology,Touch Independent Medical Education Ltd,meeting support fromNovartis,Roche,Pfizer, AstraZeneca,Daiichi Sankyo,BI,MiRXES,BMS,MSD,Abbvie,Zai Lab,Liangyihui,advisory boardforAbbVie Inc.,ACEA Pharma,Amgen,AstraZeneca,Alentis Therapeutics AG,BerGenBio ASA,Berry Oncology,Blueprint Medicines Corporation,Boehringer Ingelheim,Bowtie Life Insurance Co Ltd,Bristol Myers Squibb,C4 Therapeutics Inc,Covidien LP,CStone Pharmaceuticals,Curio Science,D3 Bio Ltd.,Daiichi Sankyo Inc.,Eisai,Fishawack Facilitate Ltd.,G1 Therapeutics Inc.,Gilead Sciences Inc.,Gritstone Oncology Inc,Guardant Health,geneDecode Co. Ltd. (uncompensated),Hengrui Therapeutics Inc.,HutchMed,Ignyta Inc.,Incyte Corporation,Imagene AI Ltd.,Inivata,IQVIA,Janssen,Lakeshore Biotech,Lily,Loxo-Oncology Inc.,Lunit Inc,Merck Serono,Merck Sharp & Dohme,Mirati Therapeutics Inc.,MiRXES Group,Novartis,OrigiMed,Pfizer,Prenetics Global Limited,Puma Biotechnology Inc.,Roche/Genentech,Regeneron Pharmaceuticals Inc,Sanofi-Aventis R&D,SFJ Pharmaceutical,Simcere of America Inc.,Simcere Zaiming, Inc.,Takeda,Vertex Pharmaceuticals,Virtus Medical Group,XENCOR, Inc,Yuhan Corporation,being member in the Board of DirectorsforAstraZeneca PLC,HutchMed,Aurora,Insighta,holding stock / stock optionofAstraZeneca,Aurora Tele-Oncology Ltd.,Biolidics Ltd.,HutchMed,Prenetics Global Limited,D3 Bio,Lunit,Bowtie Life Insurance, Lakeshore Biotech Ltd,Loxo-oncology,Virtus Medical Group,Yinson Capital Pte. Ltd.,Phanes Therapeutics, Inc.,Insighta,Alentis Therapeutics AG, outside the submitted work. Dr Li reports grants from Gilead, MSD and Astra Zeneca, honoraria from Astra Zeneca, Novartis, Amgen, Pfizer. Takeda, ACE Oncology, Merck, Guardant Health, Gilead, Janssen and MSD, meeting support from Astra Zeneca, Pfizer, Daiichi Sankyo, MSD, Amgen, advisory board for Astra Zeneca, Pfizer, AnHeart Therapeutics, Amgen, Takeda, Yuhan and Blossomhill therapeutics, outside the submitted work. No other conflicts of interest were declared.]., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)