Let me start out by saying I really like tomatoes in every way, shape, and form with the exception of ketchup used as a disguise. Further, it's a science fact that condiment discussion inflames the passions.
(ETA: The reason I looked at the Telegraph article was that I was genuinely curious.)
"Eating tomato sauce two or more times a week reduces a man’s risk of developing prostate cancer by around 20 per cent, Invalid Link Removed of 47,000 men."
As a former long term Australian resident, I can say with certainty tomato sauce is not the same as ketchup; I don't know if the Telegraph reporter was being sloppy with terminology. Further, the Harvard Med Watch linked up above in the article is not the 2002 study, but rather deals with replacing animal fats and refined carbs as the way to prostate health. Key finding:
The findings suggest that a key dietary step to fight prostate cancer is replacing animal fats and refined carbohydrates with healthier vegetable fats from foods such as avocados, walnuts, and soybean, canola, and olive oils. Men who do this may be less likely to develop aggressive and more dangerous prostate cancer, as opposed to the slow-growing, low-risk type that many men die with but not from.
And for what it's worth, the Telegraph was Boris Johnson's former employer.