We're on HN, so I hope to pull on technicality and not get _completely_ bashed ;-)
OP mentioned (and I didn't check) that 2/3 of incidents are non-controllable, and not that we can't control 2/3 of causes, that's completely different. I'm going to naïvely assume that it's much harder to have a clean slate (no meat, no pollution etc., healthy lifestyle etc.) than to live in carcinogenic to some degree environment.
As a thought exercise I'm assuming (completely sucked out of the finger) numbers in which 95% of population lives in carcinogenic environment and 5% has a clean slate. 2/3 cases being uncontrolled in such heavily swayed population would pretty much make any control pointless. If I remember correctly there's a method for calculating this, but I long forgot it. For comparison regarding chance perception "casino always wins" relates to a 1-5% house edge on games, and here we're talking about potential 33.3%.
Current knowledge is that human body consist of dozens trillions of cells which regenerate on variable rate (some couple days, some couple years). There's quite a lot of times where chance can go sideways and spawn something you don't want.
Those numbers are completely offtopic and without any base whatsoever (and once again, I didn't verify OPs claims). Spiraled on numbers :)
yes, but much of it may be out of your control. See earlier post on air pollution, likewise water pollution, and add any number of other environmental impacts. Some of which you can mitigate through personal choice, but there is also a case that these are societal problems which need societal/institutional solutions.
Even things that people don't usually associate with cancer have an impact, such as alcohol consumption, medication, oxidative stress caused by diet etc...
