A friend was just diagnosed with colorectal cancer, is that a serious condition?

Colon cancer: Overall very serious, but possibly treatable if favorable pathology and location.

Can be: Colon cancer and rectal cancer must be treated to get good results, and if ignored it can spread or become dangerous with bleeding or intestinal blockage. Localized cancers are removed with surgery and sometimes chemotherapy is used. Earlier and smaller cancers tend to be least "dangerous.".