He also survived colon cancer in his late 60s for the same reason and I flew out and took care of my sister after her first mastectomy with her first round of cancer. The doctors attributed my father's survival after they wrote him off for dead to my mother's care. They interviewed her on tape and changed the practices at their clinic based on what she had to say. From what I gather, two different cancer clinics began offering patients German Penaten cream to help their surgical scars heal because that was why my father's 16 inch surgical scar did so well.
I have zero reason to believe you are correct. There are some differences between different diseases. But my life's experience suggests that a) getting fed right b) getting proper care from someone who actually cares about you and c) adequate control over your environment are pretty universal beneficial, regardless of your exact diagnosis.
(But I'm just a woman, so not likely to be listened to. Yes, I'm feeling pretty bitter about that at the moment.)