What do you suggest if my father is 81 yrs old w prostate cancer stage 3. people keep saying to me it won't kill him. but it can kill you right?

Not low risk: Stage 3 prostate cancer should be addressed, unless your father has no symptoms from this and has a limited life expectancy from another medical condition. People are often mistaken by thinking NO MEN die from prostate cancer, but ~30,000 per year do die from it. Low risk prostate cancer often can be observed and not treated, but this is not true for stage 3 prostate cancer.

81 yo: Depending on his PSA, Gleason score and overall health that determines treatment. While MOST 81 yo won't require treatment if they have LOW RISK cancer ; if they have high risk and hey are very healthy treatment of some kind may prolong the Pts life and can be done in a way NOT to impact life quality !