Experts at Seoul National University in South Korea found that cancer victims responded well to an anti-tumour drug if their ring finger was shorter than the index finger - next to the thumb.
Doctors who tested the theory on 142 volunteers found those with short ring fingers responded better to dutasteride, a drug that fights cancer by blocking the effects of testosterone on the prostate, the 'Daily Mail' reported.
Several studies show finger length is linked to the risks of conditions ranging from heart disease and osteoarthritis to depression and Motor Neurone Disease.
The difference between the two fingers is determined by exposure to testosterone while a baby is still in the womb.
Men tend to have a longer ring finger while women tend to have ring and index fingers that are similar in length. But it can vary considerably from one person to another.
The latest findings suggest doctors might soon be able to predict who will respond best to treatment by measuring men's fingers.
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Although the men in the study did not have cancer, they did have enlarged prostates or benign prostatic hyperplasia, a common condition in men over 50 where the prostate grows and blocks the flow of urine.
Dutasteride has been used for several years to treat BPH and prostate cancer. The volunteers took the drug every day for six months.
When their prostate glands were measured to see if they had shrunk, there was a much bigger reduction in men with short ring fingers.
"These results suggest finger length might predict the response to dutasteride treatment," a report in the British Journal of Urology said.