Pathological tumor infiltrative pattern and sites of initial recurrence in stage II/III gastric cancer: Propensity score matching analysis of a multi‐institutional dataset

BACKGROUND: Advanced gastric cancer frequently recurs even after radical resection followed by adjuvant chemotherapy. The aim of this study was to evaluate the relationship between pathological infiltrative pattern (INF) and initial recurrence patterns in patients with stage II/III gastric cancer using a large multicenter database. METHODS: We retrospectively analyzed 1098 eligible patients who underwent curative gastrectomy for stage II/III gastric cancer at nine institutions between 2010 and 2014. Patients were categorized into the INF‐a/b and INF‐c groups and adjusted using propensity score matching. RESULTS: After propensity score matching, 686 patients (343 for each) were classified in the INF‐a/b and INF‐c groups. There were no significant differences in overall and disease‐free survival between the two groups. In the INF‐a/b group, frequencies of recurrence at the peritoneum, lymph node, and liver were equivalent. In contrast, the peritoneum was the most frequent site and accounted for 60% of the total recurrences in the INF‐c group. The cumulative peritoneal recurrence rate was significantly higher in the INF‐c group than in the INF‐a/b group (hazard ratio 2.47). INF‐c was a significant risk factor for peritoneal recurrences in most subgroups including age, sex, macroscopic type, tumor differentiation, and disease stage, and whether the postoperative treatment was given. Multivariate analysis identified INF‐c as an independent risk factor for peritoneal recurrences. The cumulative liver recurrence rate was significantly higher in the INF‐a/b group than in the INF‐c group (hazard ratio 3.44). CONCLUSIONS: INF may represent an important predictor of recurrence patterns after curative resection of stage II/III gastric cancer.