Prognostic factors for cytology-positive gastric cancer: a multicenter retrospective analysis.

BACKGROUND The prognosis of patients with gastric cancer and positive peritoneal lavage cytology is poor, even after gastrectomy. Though the standard therapy for this population is radical gastrectomy followed by S-1 chemotherapy, treatments vary among institutions and eras. We conducted a multicenter retrospective study to investigate the prognostic factors for cytology-positive gastric cancer. METHODS We reviewed the medical records obtained from 6 institutions, covering 2000-2019. There were 128 patients with positive cytology and no other distant metastases that underwent R1 gastrectomy. Univariate and multivariate analyses to identify prognostic factors for overall survival were conducted using Cox's proportional hazards models. RESULTS The median overall survival time was 18.6 months. In univariate analyses, age (≥ 80 years vs. < 70 years), performance status (2, 3 vs. 0), prognostic nutritional index (< 35 vs. ≥ 40), the extent of lymphadenectomy (D1 vs. ≥ D2), macroscopic type (type 4 vs. non-type 4), and postoperative chemotherapy (none vs. S-1) were significantly correlated with worse survival. Multivariate analysis revealed that lymph node metastasis (pN3b vs. pN0, hazard ratio 4.46, 95% confidence interval 1.17-16.9, p = 0.03) and postoperative chemotherapy (none vs. S-1, hazard ratio 2.28, 95% confidence interval 1.16-4.45, p = 0.02) were independent risk factors for death. No postoperative chemotherapy regimen showed a survival benefit over S-1 monotherapy. CONCLUSIONS Massive lymph node metastasis was an independent risk factor in cytology-positive gastric cancer. Postoperative chemotherapy was also an independent prognostic factor, though the most beneficial regimen was still uncertain.