Is this colon cancer?

My uncle was hospitalized due to diabetes compliciations resulting in the amputation of one of his feet. However, he is in rehab (learning how to walk again, etc) and is experiencing extreme weight loss and diarrhea so bad that he often has accidents. He lost 14 pounds last week, as of this week (reported yesterday) lost 16 pounds and today we got a phone call saying he lost 3 more pounds since yesterday (overnight). As for the diarrhea he is no where near the age to have accidents, and he's 61 and probably has never been screened for colon cancer. Also, the diarrhea has been going on for weeks!! Does anyone agree with the idea that this is colon cancer or do any of you have an idea of what this could be?