It's easy to look at cancer rates and blame it on flying, but what is more difficult is to actually separate the "flying" part of the job from other factors that may increase risk.
I recall the study done on Icelandic crews that showed higher rates than the general population in Iceland, but how do you separate out the flying from the fact that Icelandic crews are spending more time laying in the sun and out "playing" in the sun in more equatorial parts of the world?
Problem is that pilots and f/a's also have more opportunity to be "out in the sun" then do people in other jobs.