You can't analyse every activity to that degree Mart.
Essentially, cycling is very good for your overall health, as, for instance, is good old plain walking. Excessive excersise may be OK for you whilst you are young and good preparation for your older years but too much strenuous activity in your seventies is not a good idea.
Prostate cancer, thankfully, is very slow growing and will affect one in three men in their seventies or eighties, but may not usually be life threatening.