Scientists have produced evidence linking high cholesterol levels to a raised risk of prostate cancer.
Prostate cancer is treated with radiotherapy
The Italian researchers, who analysed data on 2,745 men, say more work is needed to establish a firm association.
However, they believe the key may be that cholesterol is used by the body to produce male hormones which have been linked to prostate cancer.
Other experts said the Annals of Oncology study findings were plausible, but disputed the hormone theory.
The researchers, from the Istituto di Ricerche Farmacologiche Mario Negri in Milan, admitted the study had to rely on patients reporting details of their own medical conditions.
However, they said the apparent association between high cholesterol and prostate cancer seemed to be a real one - particularly as the study uncovered no evidence of a link between the disease and ten other medical conditions.
The researchers examined data on 1,294 men with prostate cancer, and 1,451 men admitted to hospital with non-cancerous conditions.
They found men with prostate cancer were around 50% more likely to have had high cholesterol levels.
The association was particularly strong among men diagnosed with prostate cancer before the age of 50, and after the age of 65.
Both these groups were 80% more likely to report high cholesterol levels than men free from cancer.
The analysis also found prostate cancer patients were 26% more likely to have had gallstones. Thinner men appeared to be particularly vulnerable.
Researcher Dr Cristina Bosetti said: "Androgens - hormones that have a role in prostate tissue and cancer - are synthesised from cholesterol, suggesting a possible biological relationship between high cholesterol and prostate cancer.
"Gallstones are related to high cholesterol levels as well and are often composed of cholesterol.
"So, the direct relationship we found between gallstones and prostate cancer, while it was not statistically significant, suggests a similar biological mechanism may explain the link."
Dr Bosetti said there was some evidence suggesting cholesterol-lowering statin drugs may help protect against prostate cancer.
However, she said studies investigating the link had so far been limited and inconclusive.
Professor Nick James, a cancer specialist at the University of Birmingham, said it was "entirely plausible" that cholesterol was linked to prostate cancer.
He said: "There is a lot of circumstantial evidence suggesting that diet is a factor in developing prostate cancer. For instance, the disease is more common in northern European countries, where consumption of animals fats is relatively high.
"This research carries a positive message: it suggests that people can do something themselves to reduce the chances of getting a disease which is among the biggest killers of men."
However, Professor James was unconvinced by the idea that male hormones were key.
Instead, he said some of the chemicals produced by the breakdown of cholesterol were known to be carcinogenic.
Chris Hiley, of the Prostate Cancer Charity, said: "Further research is needed to confirm this but in the meantime the health benefits of a varied diet are indisputable.
"We encourage men to cut down their intake of fatty foods and red and processed meat, but continue to eat oily fish and a high fibre diet with porridge oats, as well as plenty of fresh fruit and vegetables daily."