I would heavily disagree with this - it depends entirely on the cancer you get. If it's something slow growing that would take a decade plus to kill you, sure - just trying to treat it would be worse than letting it ride.
But my father died of cancer nearing age 80, (most likely mesothelioma, though we didn't do heavy tests as it was discovered late), and it was incredibly painful and miserable for him. He had fast growing tumors in his ribs, forcing bone to spike out and hit his lungs, the tumors that grew in his lungs caused constant pneumonia and kept leaving him unable to get enough oxygen to his brain to communicate for hours at a time.
But my father died of cancer nearing age 80, (most likely mesothelioma, though we didn't do heavy tests as it was discovered late), and it was incredibly painful and miserable for him. He had fast growing tumors in his ribs, forcing bone to spike out and hit his lungs, the tumors that grew in his lungs caused constant pneumonia and kept leaving him unable to get enough oxygen to his brain to communicate for hours at a time.