Long-Term Outcomes of Patients with Gastric Cancer and Positive Peritoneal Cytology

Patients with gastric cancer and isolated positive peritoneal cytology have stage IV disease. The clinical significance of cytologic conversion is poorly understood. Our objectives are to (1) describe the clinicopathologic characteristics of patients with gastric cancer and isolated positive peritoneal cytology and their association with survival, (2) evaluate patients who underwent second cytologic evaluation for assessment of cytologic conversion, and (3) describe recurrence patterns in patients with cytologic conversion who underwent resection.

Patients with gastric adenocarcinoma and isolated positive peritoneal cytology were identified from a prospectively maintained institutional database from 1996 to 2020 for this cohort study. Patients were characterized by selection for second cytologic evaluation following chemotherapy, cytologic conversion, and selection for surgical resection. Factors associated with overall survival (OS) were evaluated by time-dependent multivariable Cox regression models.

Overall, 174 patients were identified, 62 (35.6%) were selected for second cytologic evaluation, 43 (69.4%) were cytologic converters, and 32 (74.4, 18.4% overall) underwent resection. Selection for second cytologic evaluation was associated with improved OS (hazard ratio [HR] 0.56, 95% CI 0.37-0.86), and among those patients, cytologic conversion was associated with improved OS (HR 0.17, 95% CI 0.08-0.35). Ten patients (31.3%) had no evidence of recurrence following resection during the study period. The peritoneum was the most common site of recurrence (n = 17, 53.1%).

Among patients with gastric cancer and isolated positive peritoneal cytology, second cytologic evaluation can provide prognostic information and inform treatment decisions. Cytologic conversion was documented in 25% of patients, with rare instances of long-term disease control.