Comment by freedomben

Exactly. There are definitely people who lead higher risk lives by having exposure to carcinogens, but even that has some randomness to it. I had a family friend that smoked like a chimney his entire life, and died in his late '80s with tar-filled but cancer-free lungs. Another was an x-ray tech in the earlier days before they took nearly as many precautions as they do now to protect the technicians. No cancer.

Contrast this with some aunts and uncles who lived relatively clean lives, and still ended up dying of different cancers. Sure, I don't doubt there is a cause if we dig deep into it, but there's still some randomness.