There has been some very high level research into the topic, however the last time that I read an article on it, the conclusion was that there was negligible impact on crew health, and increased cancer tended to come from sitting around the pool once at the destination.
Anyway, most of us have been exposed far more by Chenobyl and the like than radiation from space. If you are that worried about health from it, don't do it because of a more documented reason such as DVT, terrorism or fear of alien attack.