Cancer at age 78. Doubtful. The kinds of cancer I am likely to get are mostly curable now. A lot has happened in medical technology in the last 40 years. The next 40 years will most likely be no less amazing.
Cancer at 85. I dunno. Only one incident of same in my family, and both maternal grandparents and their siblings, those who lived past childhood), all lived well into their 90s. My father's side was not so long lived, but I still think it was the forced retirement at 70 that killed my paternal grandfather; he loved his work (professor). My father is now considerably older than that, still working, and enjoying it all.