Intraperitoneal Immune Checkpoint Inhibitor for Malignant Ascites

Malignant ascites appear when cancer cells metastasize to peritoneal cavity and interfere the circulation of lymph and blood. Patients with malignant ascites suffer from abdominal fullness, abdominal pain, poor intake, decreased nutrition, disability, and eventually inability to further anticancer treatment. Malignant ascites put a heavy burden on patient, their family, society and health care system. Malignant ascites from cancers of stomach, pancreas and biliary tract are more refractory to intravenous chemotherapy or intraperitoneal chemotherapy than ascites from ovarian or chemo-naïve colorectal cancers because of the inherent nature of chemoresistance. Paracentesis is a treatment with immediate effect but the ascites regrow rapidly and repetitive paracentesis puts patients on the risk of intraabdominal infection. Intraperitoneal infusion of OK-432 can reduce malignant ascites but with intolerable adverse effects of fever, chills, pain, vomiting and septation of ascites which limit the further paracentesis. Cumulating clinical experience suggests a tolerable safety profile of immune checkpoint inhibitors compared to chemotherapy for patients with malignancy. One theoretical advantage of intraperitoneal administration of immune checkpoint inhibitors is the existence of abundant inflammatory cells, immune cells and mesothelial cells dispersed in the malignant ascites. In addition, both pembrolizumab and nivolumab have been administrated intraperitoneally without obvious toxicities in murine tumor models At China Medical University Hospital, one hundred gastric cancer patients, 50 pancreatic cancer patients and 50 biliary tract cancer patients are registered and treated each year. Among them, more than 20 patients suffer from malignant ascites which will ultimately be managed by repeated paracentesis with increasing frequency. Till now, there is no reported or ongoing clinical trial to investigate the efficacy of intraperitoneal checkpoint inhibitor on the malignant ascites.