Prostate cancer is certainly more common in black African and African-Caribbean men than white men. Figures from studies in the USA suggest it may be twice as common in black men as white, and there is some evidence that in the UK there is a similar, possibly even slightly larger, difference.
Prostate cancer is very rare indeed below the age of 50 and this is true for both black and white populations. But in men between the ages of 50 and 60 the risk of prostate cancer is much greater for black African and African-Caribbean men, than white men. After the age of 60 the difference gradually begins to reduce.