I was diagnosed aged 46 years, never smoked, haven't drunk alcohol (other than maybe a glass of wine once every couple of years) for about 20 years, slim, fit and very active, no family history of it, but the only thing to increase my risk was not having had children. I do wonder if stress has played a major part - my former onc suggested I'd probably had the disease for 10-15 years. But I think getting Lyme disease 2 years before diagnosis sent it into overdrive and made it become very aggressive.
Belinda - your comment about Chernobyl is interesting. I live in Cumbria and I've often pondered the high incidence of people in the village where I lived with my parents, and the very small hamlet where I spent 16 years helping my ex on his hill farm, who have died at a young age from cancer of various types. Does make you wonder if there's a link.
