Well if you put it that way ... Just a couple of years ago it was thought that excessive coffee drinking could lead to pancreatic cancer, but that was debunked. Whew! Definitely living a healthy lifestyle will reduce the risks of cancer developing; keeping your immune system healthy will also help.
One of the reasons I finally quit smoking (13 years ago, already!) was a Scientific American article on smoking and cancer. The authors explained that independently of the carcinogenic effects of smoking, it suppresses the immune system and thus has a permissive effect on the development and growth of other cancers. I hardly smoked at all by that time, but decided that nevertheless I'd pushed my luck long enough. That could apply to most such risky practices, I think.
Exercise will also have a beneficial effect on blood pressure, digestion, etc., etc.
You know, they say that, but my friend who had cancer last year was the epitome of a health nut. Aerobics instructor, ate lots of veggies, reasonable alcohol intake, she did smoke in high school though.