Objective  To study changes in body composition in patients with locally advanced gastric cancer, before and after neoadjuvant chemotherapy, to predict the efficacy of neoadjuvant chemotherapy and evaluate the value of short-term complications and long-term prognoses.

  Methods   General, clinicopathological, and imaging data of patients with locally advanced gastric cancer who underwent neoadjuvant chemotherapy and surgery at The Affiliated Hospital of Qinghai University from January 2012 to December 2018 were collected through retrospective analyses. According to the inclusion and exclusion criteria of this study, the skeletal muscle index, subcutaneous index, and visceral fat index were evaluated. In order to reduce the selection bias as much as possible, the patient data of Union Hospital Affiliated to Fujian Medical University were selected as external verification according to the same criteria. Results Before and after receiving neoadjuvant chemotherapy, a significant difference in body composition and muscle index (P=0.023) was observed. Body composition patterns were analyzed according to the degree of pathological remission (≥50% vs. <50%). The results showed that the change in muscle index before and after neoadjuvant chemotherapy could independently predict pathological remission (odds ratio=1.308; P<0.001). In survival analyses, the difference in long-term survival of patients with different Δskeletal muscle index (ΔSMI) indicated that the overall survival (OS) of patients with ΔSMI ≥ 1.2 was significantly better than that of patients with ΔSMI<1.2 (P<0.05).

  Conclusions  ΔSMI is expected to be a simple, objective, effective, and non-invasive index for evaluating the efficacy of chemotherapy, determining the timing of surgery, and extending the OS of patients with locally advanced gastric cancer.