What will most likely happen to our friend who is ignoring his colon tumor?

My husband has known “R” for many years. R is sixty five and, I think due to stress since he doesn’t smoke or drink, has ruined his health from devoting the last ten years to taking care of his parents who are both in their nineties! His father is rude to R and ungrateful. R’s mother does not know her grandson anymore, falls down, and is simply demented. I’ve never met either of his parents. So R is renting his house and has been a live-in nurse/caretaker for years. He takes his mother to the beauty salon once a week and seven nights a week he loads her into the car with her wheelchair and takes them out to eat when he was not supposed to lift more than five pounds. So five months ago R was diagnosed with heart disease and had a quadruple bypass. His son came and stayed with the parents. Tragically, they have found a large, lemon sized tumor in R’s colon. But R can’t leave his parents to have the surgery then stay in the hospital to recuperate. He claims they have plenty of cash to stay in a nursing home just while R is in the hospital but his father won’t part with the money. Won’t that tumor just pop his colon wall? If so, won’t it kill R? R lives in a Dallas suburb and acts like the tumor will simply shrink on its own. His mother has no idea anything is wrong with R. Seems like he is giving his life to his aging parents who show zero gratitude.