I remember seeing a photo of him a Dodger game a year or two ago and people made fun of him because he was so skinny. Unfortunately in hindsight we know he was dealing with cancer.
I suspect his diagnosis came as a big surprise (being so young) and it was most likely advanced at the time of diagnosis. There must have been a family history. Screening for colon cancer is set at age 50, but a lot have pushed it to be moved back to 40. I would agree as screening and treatment are very advanced now.
Coming from a family that has had many deal with cancer (including a cousin who lost his battle at 22), I greatly admire that he continued working after his diagnosis.