Background: Immune checkpoint inhibitors (ICIs) no longer are approved for second-line or later treatment of extensive-stage small cell lung cancer (ES-SCLC), and have not been studied in combination with chemotherapy. Exploring the efficacy and safety of second-line or later immunotherapy for ES-SCLC is an urgent clinical question that needs to be addressed, and combination therapies are an important research direction. This study intended to investigate the efficacy and safety of the sintilimab in combination with chemotherapy as a second-line and beyond treatment option for ES-SCLC., Methods: Medical records of patients who received treatment with sintilimab in combination with chemotherapy or chemotherapy alone as a second-line or beyond therapy were retrospectively analyzed. The study evaluated efficacy and safety. Indicators of efficacy included objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). Safety indicators included adverse events (AEs)., Results: This cohort comprised of 46 patients: 24 in the sintilimab combination chemotherapy group and 22 in the chemotherapy group. Chemotherapy received by both groups was either albumin-bound paclitaxel or irinotecan. Compared with the chemotherapy group, the sintilimab combination chemotherapy group had higher ORR and DCR (ORR: 37.5% vs. 9.1%, P=0.04; DCR: 75.0% vs. 40.9%, P=0.04), and significantly prolonged PFS and OS [median PFS (mPFS): 5.07 vs. 2.45 months, P=0.006; median OS (mOS): 14.43 vs. 10.34 months, P=0.009]. Also, there was no significant increase in the incidence of AEs in the sintilimab combination chemotherapy group, which was well tolerated by patients., Conclusions: Sintilimab in combination with chemotherapy is superior to single-agent chemotherapeutic treatment as second-line or later therapy in ES-SCLC patients who have not received prior immunotherapy. These results need to be confirmed in future clinical trials., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-769/coif). N.S. has obtained research grants from Eli Lilly, Chugai Pharmaceutical, Taiho Pharmaceutical, Pfizer, Ono Pharmaceutical, Nippon Kayaku, Takeda Pharmaceutical, Eisai, Shionogi, Daiichi Sankyo, and Boehringer Ingelheim; and has received speaking honoraria from Eli Lilly, AstraZeneca, MSD, Chugai Pharmaceutical, Taiho Pharmaceutical, Pfizer, Ono Pharmaceutical, Nippon Kayaku, Takeda Pharmaceutical, Daiichi Sankyo, Boehringer Ingelheim, Novartis, Kyowa Kirin, and Bristol Myers Squibb. A.K.G.’s institution has received grant funding for clinical trials from Apexigen, NEKTAR Pharmaceuticals, Merck, Pfizer, Boehringer Ingelheim, Poseida Inc. and Mirati Therapeutics. A.K.G. has received royalties from Oxford University Press; and consulting fees from Jazz Pharmaceuticals, AstraZeneca, Regeneron Pharmaceuticals, Sanofi Genzyme, Cardinal Health, Flagship Biosciences, Mirati Therapeutics, Beigene Ltd., G1 Therapeutics, Blueprint Medicines and Bayer; and honoraria for lectures from Paradigm Communications, Plexus Communications and MJH Life Sciences. A.K.G. also participated in data and Safety monitoring boards for YmAbs Therapeutics, and has administrative responsibilities (uncompensated) at Academic and Community Cancer Research United and International Association for the Study of Lung Cancer. J.W.N. reports research funding from Genentech/Roche, Merck, Novartis, Boehringer Ingelheim, Exelixis, Nektar Therapeutics, Takeda Pharmaceuticals, Adaptimmune, GSK, Janssen, AbbVie, and Novocure; and personal fees for consulting and advisory from AstraZeneca, Genentech/Roche, Exelixis, Takeda Pharmaceuticals, Eli Lilly and Company, Amgen, Iovance Biotherapeutics, Blueprint Pharmaceuticals, Regeneron Pharmaceuticals, Natera, Sanofi/Regeneron, D2G Oncology, Surface Oncology, Turning Point Therapeutics, Mirati Therapeutics, Gilead Sciences, AbbVie, Summit Therapeutics, Novartis, Novocure, Janssen Oncology and Anheart Therapeutics; and honoraria from CME Matters, Clinical Care Options CME, Research to Practice CME, Medscape CME, Biomedical Learning Institute CME, MLI Peerview CME, Prime Oncology CME, Projects in Knowledge CME, Rockpointe CME, MJH Life Sciences CME, Medical Educator Consortium, and HMP Education. B.C. reports that this research was funded by the Wu Jieping Medical Foundation (No. 320.6750.2020-10-81). L.W. reports that this research was funded by the National Key Clinical Specialty Scientific Research Project (No. Z2023098), the Hunan Provincial Health High-Level Talent Scientific Research Project (No. R2023125), the Science and Technology Innovation Program of Hunan Province (Nos. 2023SK4024 and 2021SK51121), the Hunan Cancer Hospital Climb plan (No. ZX2020005-5), and the Beijing Xisike Clinical Oncology Research Foundation (No. Y-2019Genecast-024), L.W. also received personal fees from AstraZeneca, Roche, Bristol-Myers Squibb, MSD, Pfizer, Lilly, Boehringer Ingelheim, Merck, Innovent, and Hengrui, outside the submitted work. The other authors have no conflicts of interest to declare., (2024 Journal of Thoracic Disease. All rights reserved.)