Tu1797 Validation of Immediate Peritoneal Washing Cytology Results in Pancreatic and Gastric Cancer

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Introduction: The mainstay of treatment for pancreatic and gastric cancers is surgical resection. Unfortunately many of these patients present with locally advanced, unresectable or distant disease and therefore medical management may be of more benefit. Accurate staging of patients with pancreatic and gastric cancer is essential in determining the best treatment strategy. Despite preoperative imaging there remains a group of patients that have clinically occult metastatic disease. Positive peritoneal cytology is a poor prognostic indicator for survival in both gastric and pancreatic cancer. Surgical resection may not be of benefit in those with positive peritoneal cytology. At our institution, a diagnostic laparoscopy with peritoneal washings is performed prior to surgical resection. We performed a retrospective review to evaluate the accuracy of immediate peritoneal washing interpretation in both gastric cancer and pancreatic cancer. Results: There were 51 patients that underwent immediate peritoneal washing interpretations. There were 5 patients with gastric adenocarcinoma, 2 patients with cholangiocarcinoma, and 44 patients with pancreatic adenocarcinoma. Four of the patients had positive cytology for tumor cells with immediate interpretation, and 47 patients had cytology negative for tumor cells with immediate interpretation. There was only one patient with negative cytology on immediate interpretation with cytology positive for malignant cells on final pathologic results. There were many RBCs noted within the peritoneal fluid specimen, which is probably why the cancer cells were missed. Immediate peritoneal cytology results had a 100% positive predictive value, and a 97% negative predictive value. There were no false positive results. Discussion: Positive peritoneal cytology is considered a poor prognostic factor for survival in both gastric and pancreatic cancer. In pancreatic and gastric cancer, previous studies have shown resection in the presence of metastatic disease does not improve survival. Diagnostic laparoscopy has been used as an adjunct to help stage patients before proceeding with a radical resection that has an associated significant morbidity andmortality rate is futile and potentially harmful, delaying or obviating systemic therapy that may be of more benefit to the patient. Our results show that utilizing immediate interpretation of peritoneal cytology is reliable and accurate. There was only one patient with a false negative result and there were no false positive results. Therefore, prior to surgical resection immediate interpretation can be utilized. Conclusion: Diagnostic laparoscopy with peritoneal washings and immediate interpretation of cytology can be used prior to proceeding with surgical resection. A futile operation can potentially be avoided with the use of immediate interpretation of the peritoneal fluid.