Lycopene isn't very water soluble, so if you eat a raw tomato, the Lycopene mostly just passes through as fibre.
In order to absorb Lycopene, the tomatoes (including skin where it's most concentrated) need cooking in oil which will dissolve out the Lycopene, and then the oil consumed.
Good sources are tomato soup, tomato ketchup, tomato concentrate providing it contains oil (not all does).
I thought it's main claim was on reducing the incidence of prostate cancer. I've not heard of it doing any good once you've got prostate cancer, nor for shrinking the prostate, but it's not likely to do any harm.