Studies about enemas and cancer

Is anybody aware of any valid scienticic studies about regular enemas correlating to incidence of colon or other cancer ? Colon therapists claim beneficial effects of colonics but don't seem to have any backup studies of results from a population who use colonics and/or enemas on a regular basis versus people who do not use these therapies. If ther are no such studies, perhaps there is an opportunity to do so. Thanks for your input. Tweet