Background: Lung cancer is the second most common cancer and leading cause of cancer mortality worldwide. Recent advances in molecular testing and targeted therapy have improved survival among patients with metastatic non-small-cell lung cancer (NSCLC). We sought to quantify and describe molecular testing among metastatic non-squamous NSCLC cases in selected Southeast Asian countries and describe first-line therapy chosen., Patients and Methods: A retrospective study was conducted based on incident lung cancer cases diagnosed between 2017 and 2019 in Lampang (Thailand), Penang (Malaysia), Singapore and Yogyakarta (Indonesia). Cases (n = 3413) were defined using the International Classification of Diseases for Oncology third edition. In Singapore, a clinical series obtained from the National Cancer Centre was used to identify patients, while corresponding population-based cancer registries were used elsewhere. Tumor and clinical information were abstracted by chart review according to a predefined study protocol. Molecular testing of epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK) gene rearrangement, ROS1 gene rearrangement and BRAF V600 mutation was recorded., Results: Among 2962 cases with a specified pathological diagnosis (86.8%), most patients had non-squamous NSCLC (75.8%). For cases with staging information (92.1%), the majority presented with metastatic disease (71.3%). Overall, molecular testing rates in the 1528 patients with stage IV non-squamous NSCLC were 67.0% for EGFR, 42.3% for ALK, 39.1% for ROS1, 7.8% for BRAF and 36.1% for PD-L1. Among these patients, first-line systemic treatment included chemotherapy (25.9%), targeted therapy (35.6%) and immunotherapy (5.9%), with 31% of patients having no record of antitumor treatment. Molecular testing and the proportion of patients receiving treatment were highly heterogenous between the regions., Conclusions: This first analysis of data from a clinically annotated registry for lung cancer from four settings in Southeast Asia has demonstrated the feasibility of integrating clinical data within population-based cancer registries. Our study results identify areas where further development could improve patient access to optimal treatment., Competing Interests: Disclosure RS is involved in advisory boards for Amgen, AstraZeneca, Bayer, BMS, Boehringer Ingelheim, Janssen, Lily, Merck, Merck Serono, Novartis, Pfizer, Puma, Roche, Taiho, Takeda, Yuhan and has received research grants from AstraZeneca and Boehringer Ingelheim. RK has been an advisor/speaker or received honorarium from AstraZeneca, Pfizer, Merck, MSD, BMS, J&J, Ipsen, Eisai, Amgen, Novartis, Lucence Therapeutics and Astellas. NP has consulting or advisory roles with AstraZeneca, Novartis and Roche. SP has consulting/advisory roles with AbbVie, Amgen, Arcus, AstraZeneca, Bayer, Beigene, Biocartis, BioInvent, Blueprint Medicines, Boehringer Ingelheim, Bristol-Myers Squibb, Clovis, Daiichi Sankyo, Debiopharm, ecancer, Eli Lilly, Elsevier, F-Star, Fishawack, Foundation Medicine, Genzyme, Gilead, GSK, Illumina, Imedex, IQVIA, Incyte, iTeos, Janssen, Medscape, Merck Sharp and Dohme, Merck Serono, Merrimack, Novartis, Novocure, Oncology Education, Pharma Mar, Phosplatin Therapeutics, PER, Pfizer, PRIME, Regeneron, RMEI, Roche/Genentech, RTP, Sanofi, Seattle Genetics, Takeda and Vaccibody; has talked in organized public events for AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, ecancer, Eli Lilly, Foundation Medicine, Illumina, Imedex, Medscape, Merck Sharp and Dohme, Mirati, Novartis, PER, Pfizer, Prime, Roche/Genentech, RTP, Sanofi and Takeda; has been a principal investigator in trials (institutional financial support for clinical trials) sponsored by Amgen, AstraZeneca, Beigene, Bristol-Myers Squibb, GSK, Merck Sharp and Dohme, and Roche/Genentech. RSt has been an invited speaker for Amgen, AstraZeneca, Blueprint, Bristol-Myers Squibb, Boehringer Ingelheim, GSK, MSD, Novartis and Roche; has been on advisory boards for AstraZeneca, BMS, Boehringer Ingelheim, GSK, MSD, Pfizer, Roche, Sandoz, Seattle Genetics and Takeda; has received institutional support (ETOP, IBCSG) from AstraZeneca, Bristol-Myers Squibb, Daiichi Sankyo, Celgene, Ipsen, Janssen, Mirati, MSD, Novartis, Pfizer, Pierre Fabre and Roche. All other authors have declared no conflicts of interest. Where authors are identified as personnel of the International Agency for Research on Cancer/World Health Organization, the authors alone are responsible for the views expressed in this article, and they do not necessarily represent the decisions, policy, or views of the International Agency for Research on Cancer/World Health Organization., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)