A study of hospital patients found those whose ring finger on the right hand was significantly longer than the index finger were more likely to get the disease than those fingers were roughly same length.
A long ring finger is thought to result from higher exposure to the hormone testosterone while in the womb.
Previous research has suggested a long ring finger could be beneficial, having been linked to a reduced risk of heart disease and increased fertility.
More than 30,000 men are diagnosed with prostate cancer every year, equivalent to more than one an hour. Bob Monkhouse, the comedian who died from the disease in 2003, has posthumously featured in a fund-raising campaign by the Prostate Cancer Research Foundation that includes a Twitter account for his jokes.
The latest study, carried out at Gachon University Gil Hospital, in Incheon, South Korea, and reported in the Daily Mail, looked at 366 men over the age of 40 who went to a hospital clinic complaining of problems urinating, a symptom which could be a warning sign of cancer.
Blood tests showed that men whose ring fingers were much longer than their index finger, next to the thumb, had almost double the normal levels of prostate specific antigen, a chemical sometimes found in high levels in blood when cancer is present.
Three times as many of these men went on to be diagnosed with prostate cancer.
However, Ed Yong, head of health information for Cancer Research UK, told the newspaper that results of the study should be treated with caution.
He said: “Finger length ratios have been linked to all sorts of things before with little evidence that measuring these ratios will ever actually be useful.
“For example, this very small study finds an association between finger length ratio and prostate cancer risk, but tells us nothing about whether the ratio can be used to reliably predict that risk.”
