Risk of peritoneal metastases in patients who had negative peritoneal staging and received therapy for localized gastric adenocarcinoma

Background: Positive peritoneal cytology (+PCyt) or gross carcinomatosis (GPC) carries a poor prognosis. Laparoscopic staging to detect +PCyt/GPC is recommended for all ≥T1b gastric adenocarcinoma (GAC). The natural history of patients with GAC who have baseline −PCyt and then undergo multimodality therapy is not well documented, particularly for the risk of subsequent GPC. Methods: We identified 238 GAC patients with baseline −PCyt who were followed for the development of peritoneal carcinomatosis (PC). Standard statistical methods were employed. Results: Of 238 patients, 192 had attempted surgery after preoperative therapy. Of these, 13 patients (6.8%) had GPC and one had liver metastases, thus surgery was aborted. We followed 164 patients who had an R0 resection. The median follow-up duration was 3.4 (range, 0.6-18) years. The rate of PC was 13.4%, (22/164 patients) and the median time to PC was 15.6 months. Female gender was associated with PC on multivariate analysis. The 5-year OS rate for patients without subsequent PC was 75%. Conclusion Even with baseline −Cyt, ∼25% of patients develop PC following multimodality therapy. Patients who do not develop PC have an excellent OS rate. Further research is warranted to detect PC at baseline by the use of biomarkers.