Several reports have assessed the clinical characteristics of elderly patients aged 85 years or older who had gastric cancer. However, there are only a few reports targeting patients aged ≥ 90 years.

This multi-institutional study included 596 elderly patients with gastric cancer who were treated surgically between 2000 and 2021. The clinicopathological characteristics and long-term prognosis of two patient groups 85–89-year-old group (85–89 group, n = 496) and ≥ 90-year-old group (90 + group, n = 100) were compared.

The 90 + group had a significantly lower overall survival and disease-specific survival than the 85–89 group. Based on the multivariate analysis, in the 85–89 group, American Society of Anesthesiologists physical status score of 3 (P < 0.01), stage III/IV disease (P < 0.01), reduced extent of dissection (P = 0.04), and Clavien-Dindo grade III or higher complication (P = 0.02) were independent poor prognostic factors. Further, in the 90 + group, male sex (P < 0.01), low prognostic nutritional index (< 40) (P = 0.02), and total gastrectomy (P < 0.01) were independent poor prognostic factors.

The poor prognostic factors differed between the 85–89 group and 90 + group. In the 90 + group, male sex, low prognostic nutritional index, and total gastrectomy were associated with overall survival. These factors may aid postoperative risk stratification and surgical planning in this age group, but do not by themselves determine surgical candidacy.