Neoadjuvant Nab-Paclitaxel Plus Oxaliplatin, S-1, and Sintilimab in Early-Onset Resectable Gastric Cancer

This study aims to evaluate the effectiveness and safety of a preoperative treatment (called neoadjuvant therapy) combining four drugs-nab-paclitaxel, oxaliplatin, S-1, and sintilimab-for patients with locally advanced, resectable early-onset gastric cancer (diagnosed at age 45 or younger). All participants will receive this drug combination before undergoing surgery to remove the tumor. The goal is to shrink the tumor, increase the chance of complete surgical removal, and improve long-term outcomes. This is a single-arm, open-label, phase II clinical trial, meaning all participants will receive the same treatment, and both doctors and patients will know what drugs are being used. The study is being conducted at Peking University People's Hospital.