[tomhoward]

This article of his "Top Ten Reasons Not to Run Marathons" has citations for each of the supposed risks, including cancer.

http://www.arthurdevany.com/articles/20091028

I think the lack of citations is because it's a concentrate of his theories & discoveries. Individual articles (many of which are paywalled, sadly) seem to have better references. It'll be interesting to see how well referenced his book is.

[rsheridan6]

All he mentioned was that a few markers associated with cancer are elevated in marathon runners. The actual markers indicate inflammation and a leaky blood brain barrier, which could be caused by lots of things besides cancer.