There is a very specific study about prostate cancer and family history in the most recent issue of the Journal of Radiation Oncology Biology Physics. The researchers studied whether there was an effect on the treatment outcomes of prostate cancer patients who used brachytherapy (seeding the prostate with radiation) if they had a first degree family history of prostate cancer.
In other words Bob's dad Stan had prostate cancer. If Bob has prostate cancer and uses seed implants will he do as well as someone who does not have this family history.
The good news is that there appears to be no significant difference in outcomes between Bob and all other men who have prostate cancer without a family history. This is good because it allows a higher dose of radiation to treat a small area and in a shorter amount of time.
By the way, if radiation oncology is something you are interested in this is the journal for you with information on a broad variety of cancers from bone to spinal cord and back again. You can read the abstracts for free.