Nivolumab and Ipilimumab in Mucinous Colorectal and Appendiceal Tumors

Inclusion Criteria: * Subjects must have signed and dated an IRB-approved written informed consent form prior to the performance of any protocol-related procedures that are not part of standard care. * Colorectal or appendiceal mucinous adenocarcinoma with peritoneal-only metastatic disease. It is recognized that in some patients, peritoneal disease will predominate without distinction of the site of origin, and such patients will be eligible. * Microsatellite stable by PCR and/or mismatch repair proficient by immunohistochemistry * ECOG performance status of 0 or 1 * Prior therapy with a fluoropyrimidine, oxaliplatin, and irinotecan unless contraindicated or refused. Prior treatment with antiangiogenic and/or anti-EGFR antibody therapy is permitted but not required * Measurable disease by RECIST v. 1.1 * Laboratory parameters: * Absolute neutrophil count \> 1500/μL * Platelets \> 100,000/μL * Hemoglobin \> 9.0 g/dL * PT/INR or PTT \< 1.5xULN * Creatinine \< 1.5xULN OR creatinine clearance \> 50 mL/min by Cockcroft-Gault formula * Total bilirubin \< 1.5xULN * Subjects with Gilbert's Syndrome must have a total bilirubin level of \< 3.0xULN * Albumin \> 3.0 g/dL * AST and/or ALT: \< 3.0×ULN * Subjects with HIV are permitted provided they meet the following criteria: * CD4+ cell count \> 250 cells/mm3 * No history of AIDS-defining conditions other than low CD4+ count * If subject is on antiretroviral therapy, there must not be expected significant drug…