Exercise can apparently lessen the rate of cancer cell growth and even help prevent its recurrence.

I didn't have radiation and was diagnosed with AF about two thirds of the way through chemo. Both my cardiologist and my oncologist were of the opinion that A/C may have been a contributing factor. I was certainly advised that herceptin could cause damage to the heart wall (in my case it did not). Four and a bit years on I think the AF was due to a combination of things including age, surgery and chemo. It's hard to advise people about everything that's possible - the written material I got about both chemotherapies was scary enough! - particularly when the chances of something happening may be low. If I had been told beforehand, I am not at all sure what I would have done as I would have imagined I might have to live very quietly. In fact my AF is utterly manageable, I am practically symptom free, take a couple of tablets and live normally. It's all so variable and individual.