 This pilot clinical trial studies how well carbon C 14 oxaliplatin microdosing assay works in predicting exposure and sensitivity to oxaliplatin-based chemotherapy in patients with colorectal cancer that has spread to other places in the body and usually cannot be cured or controlled with treatment. Drugs used in chemotherapy, such as oxaliplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Carbon C 14 is a radioactive form of carbon, exists in nature and in the body at a low level. Microdose carbon C 14 oxaliplatin diagnostic assay may help doctors understand how well patients respond to treatment and develop individualize oxaliplatin dosing in patients with colorectal cancer. 