I remember reading that priests, monks etc showed a higher incidence of prostate cancer due to abstinence but I have not been able to find it again.
just off the press. For example, men who reported 21 or more ejaculations per month in their 40s had a 32% lower risk of prostate cancer later in life compared with those who reported between four and seven ejaculations per month. Men who reported more than 21 monthly ejaculations in the previous year had a 51% lower risk of prostate cancer.

Overall, an average of 21 or more ejaculations a month during a man's lifetime decreased the risk of prostate cancer later in life by 33%. And each increase of three ejaculations per week during a man's lifetime was associated with a 15% reduction in prostate cancer risk.
Ejaculation May Lower Prostate Cancer Risk

The findings, published in the April 7 issue of The Journal of the American Medical Association, are based on data collected from nearly 30,000 predominately white men aged 46 to 81.