Firstly Remi Abiola, (don't think she would have been smoking), Sonique, Paul Dairo and so many others. What's going on?

Do vitamins (like multivitamins and vitamin C) help to prevent cancer at an early stage?
How can one be really sure and secure enough to prevent cancer? Cancer of anything whether the breasts, lungs, kidneys, blood etc. Perhaps you eat healthy, exercise daily, take your vitamins,stay healthy(away from smoking and such), Is cancer still likely to occur?