I am addicted to Stand Up Paddle boarding and I will be working with an exercise physiologist to get me back on my board as soon as possible. Whilst exercise does not prevent cancer, I fully believe that exercise increases your mental attitude to everything in your life and will be extremely useful for what will be going through from your diagnosis, surgery and treatment. The catalyst program in May 2016 (link below) is very interesting to watch for the correlation between exercise and health during treatment ( I have done lots of Google/ research on exercising during treatment)
http://www.abc.net.au/catalyst/stories/4459555.htmAt the end of the day, whatever gets you through this time of your life is what you need to do