General information of the included studies.

IntroductionLung cancer is the primary cause of cancer-related deaths worldwide, with high rates of morbidity and mortality. The most effective treatment for early stage (I-II) non-small cell lung cancer (NSCLC) is surgical resection. However, the extent of mediastinal lymph nodes removal required and the impact of their removal remains controversial. This systematic review and meta-analysis aimed to evaluate the postoperative complications in patients with stage I-II NSCLC who received mediastinal lymph node dissection (MLND) or mediastinal lymph node sampling (MLNS).Methods and analysisAccording to the predefined inclusion criteria, we will conduct a comprehensive search for randomized controlled trials (RCTs) and observational studies examining the postoperative complications of MLND compared to MLNS in patients with stage I-II NSCLC. The search will be performed across multiple databases including PubMed, Embase, the Cochrane Library, CNKI, WanFang, Sinomed, VIP, Duxiu, and Web of Science from inception to February 2024. Additionally, relevant literature references will be retrieved and hand searching of pertinent journals will be conducted. Screening, data extraction, and quality assessment will be performed by two independent reviewers. Review Manager 5.4 will be applied in analyzing and synthesizing. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) will be used to assess the quality of evidence for the whole RCTs and used Newcastle-Ottawa scale to assess the methodologic quality of observational studies.Ethics and disseminationThis study did not include personal information. Ethical approval was not required for this study. This study is based on a secondary analysis of the literature, so ethical review approval is not required. The final report will be published in a peer-reviewed journal.ConclusionThis systematic review will contribute to compare the safety and survival benefits of these two surgical techniques for the treatment of early stage NSCLC, to further guide the selection of surgical approaches.Trial registrationThe protocol of the systematic review has been registered on Open Science Framework, with a registration number of DOI https://doi.org/10.17605/OSF.IO/N2Y5D.</div

PRISMA-P-checklist.

IntroductionLung cancer is the primary cause of cancer-related deaths worldwide, with high rates of morbidity and mortality. The most effective treatment for early stage (I-II) non-small cell lung cancer (NSCLC) is surgical resection. However, the extent of mediastinal lymph nodes removal required and the impact of their removal remains controversial. This systematic review and meta-analysis aimed to evaluate the postoperative complications in patients with stage I-II NSCLC who received mediastinal lymph node dissection (MLND) or mediastinal lymph node sampling (MLNS).Methods and analysisAccording to the predefined inclusion criteria, we will conduct a comprehensive search for randomized controlled trials (RCTs) and observational studies examining the postoperative complications of MLND compared to MLNS in patients with stage I-II NSCLC. The search will be performed across multiple databases including PubMed, Embase, the Cochrane Library, CNKI, WanFang, Sinomed, VIP, Duxiu, and Web of Science from inception to February 2024. Additionally, relevant literature references will be retrieved and hand searching of pertinent journals will be conducted. Screening, data extraction, and quality assessment will be performed by two independent reviewers. Review Manager 5.4 will be applied in analyzing and synthesizing. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) will be used to assess the quality of evidence for the whole RCTs and used Newcastle-Ottawa scale to assess the methodologic quality of observational studies.Ethics and disseminationThis study did not include personal information. Ethical approval was not required for this study. This study is based on a secondary analysis of the literature, so ethical review approval is not required. The final report will be published in a peer-reviewed journal.ConclusionThis systematic review will contribute to compare the safety and survival benefits of these two surgical techniques for the treatment of early stage NSCLC, to further guide the selection of surgical approaches.Trial registrationThe protocol of the systematic review has been registered on Open Science Framework, with a registration number of DOI https://doi.org/10.17605/OSF.IO/N2Y5D.</div

Flow diagram showing the selection process of articles.

*Consider, if feasible to do so, reporting the number of records identified from each database or register searched (rather than the total number across all databases/registers). **If automation tools were used, indicate how many records were excluded by a human and how many were excluded by automation tools. From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi: 10.1136/bmj.n71 For more information, visit: http://www.prisma-statement.org/.</p