ImportanceThe survival benefit of laparoscopic total gastrectomy combined with spleen-preserving splenic hilar lymphadenectomy (LSTG) for locally advanced proximal gastric cancer (APGC) without invasion into the greater curvature remains uncertain.ObjectiveTo compare the long-term and short-term efficacy of LSTG (D2 + No. 10 group) and conventional laparoscopic total gastrectomy (D2 group) for patients with APGC that has not invaded the greater curvature.Design, Setting, and ParticipantsIn this open-label, prospective randomized clinical trial, a total of 536 patients with clinical stage cT2 to 4a/N0 to 3/M0 APGC without invasion into the greater curvature were enrolled from January 2015 to October 2018. The final follow-up was on October 31, 2021. Data were analyzed from December 2021 to February 2022.InterventionsEligible patients were randomized to the D2 + No. 10 group or the D2 group.Main Outcomes and MeasuresThe primary outcome was 3-year disease-free survival (DFS). The secondary outcomes were 3-year overall survival (OS) and morbidity and mortality within 30 days after surgery.ResultsOf 526 included patients, 392 (74.5%) were men, and the mean (SD) age was 60.6 (9.6) years. A total of 263 patients were included in the D2 + No. 10 group, and 263 were included in the D2 group. The 3-year DFS was 70.3% (95% CI, 64.8-75.8) for the D2 + No. 10 group and 64.3% (95% CI, 58.4-70.2; P = .11) for the D2 group, and the 3-year OS in the D2 + No. 10 group was better than that in the D2 group (75.7% [95% CI, 70.6-80.8] vs 66.5% [95% CI, 60.8-72.2]; P = .02). Multivariate analysis revealed that splenic hilar lymphadenectomy was not an independent protective factor for DFS (hazard ratio [HR], 0.86; 95% CI, 0.63-1.16) or OS (HR, 0.81; 95% CI, 0.59-1.12). Stratification analysis showed that patients with advanced posterior gastric cancer in the D2 + No. 10 group had better 3-year DFS (92.9% vs 39.3%; P < .001) and OS (92.9% vs 42.9%; P < .001) than those in the D2 group. Multivariate analysis confirmed that patients with advanced posterior gastric cancer could have the survival benefit from No. 10 lymph node dissection (DFS: HR, 0.10; 95% CI, 0.02-0.46; OS: HR, 0.12; 95% CI, 0.03-0.52).Conclusions and RelevanceAlthough LSTG could not significantly improve the 3-year DFS of patients with APGC without invasion into the greater curvature, patients with APGC located posterior gastric wall may benefit from LSTG.Trial RegistrationClinicalTrials.gov Identifier: NCT02333721