 - Patients should have microsatellite stable MSS tumor by polymerase chain reaction PCR assay or mismatch repair protein proficient MMRP tumor by immunohistochemistry as confirmed by the presence of MLH1, MSH2, MSH6, and PMS2; the diagnosis of colorectal cancer should be confirmed by pathology either on the primary tumor or from a prior biopsy of a metastatic disease site 