Snow presumably had access to the latest and best treatments for colon cancer. Yet he died just three years from diagnosis. His disease was apparently localized disease at diagnosis. He received adjuvent therapy to prevent recurrence. It failed as it does in about 1/3 of patients so treated, and his cancer recurred with metastatic disease just over a year ago.
You may hear all manner of propaganda about new advances from big Pharma, new drug regimens, miracle biologic agents that cost thousands of dollars a month, and improvements of survival. You need to remember however that the advances improve survival minimally (in advanced disease about two months) at great financial cost.
The lesson if there is one is that the best approach is prevention (for those cancers so amenable) and early diagnosis. Colonoscopy should be a part of health maintenance for everyone, particularly if there is a family history of colon cancer.