There will be other factors as well. The Chinese, Japanese and other Far Eastern peoples tend not to eat pre-prepared meals or foods that have been wrapped in plastic, and their Governments do not add flouride or other chemicals to tap water. The same can be said of mediterranean folk who also have far lower rates of PCa.
When I was having genetic counselling in relation to our family line of brain tumours, these were the issues identified to me by the geneticist as possibly increasing risk - plastics (including cling film), drinking water, radiation exposure (including microwaves), living in areas of naturally occurring radon, living on pylon lines, etc. At the oncology dept, John was told off by a nurse for having his mobile phone in his shirt pocket - she said you never see oncology professionals carrying their phones near major organs.
Clearly, as most of my forebears lived and worked in a very small geographic area (a large family all residing in the same few streets in the North East and almost all working in the shipyard or down the mines) and will have breathed the same air, eaten the same food, cooked in similar ways and drunk the same water, there was just as much chance that it was their life style that had caused the brain tumour as it being a rogue family gene. In our village (which has had a huge number of brain tumours recently although not enough apparently to count in DoH data as an official cluster) you can plot their houses on a precise straight line through the village. We also have quite a lot of young onset PCa in the village.