NEW YORK, N.Y. - A huge international effort involving more than 100 institutions and genetic tests on 200,000 people has uncovered dozens of signposts in DNA that can help reveal further a person's risk for breast, ovarian or prostate cancer, scientists reported Wednesday.

It's the latest mega-collaboration to learn more about the intricate mechanisms that lead to cancer. And while the headway seems significant in many ways, the potential payoff for ordinary people is mostly this: Someday there may be genetic tests that help identify women with the most to gain from mammograms, and men who could benefit most from PSA tests and prostate biopsies.

And perhaps farther in the future these genetic clues might lead to new treatments.

"This adds another piece to the puzzle," said Harpal Kumar, chief executive of Cancer Research U.K., the charity which funded much of the research.

One analysis suggests that among men whose family history gives them roughly a 20 per cent lifetime risk for prostate cancer, such genetic markers could identify those whose real risk is 60 per cent.

The markers also could make a difference for women with BRCA gene mutations, which puts them at high risk for breast cancer. Researchers may be able to separate those whose lifetime risk exceeds 80 per cent from women whose risk is about 20 to 50 per cent. One doctor said that might mean some women would choose to monitor for cancer rather than taking the drastic step of having healthy breasts removed.

Scientists have found risk markers for the three diseases before, but the new trove doubles the known list, said one author, Douglas Easton of Cambridge University. The discoveries also reveal clues about the biological underpinnings of these cancers, which may pay off someday in better therapies, he said.

Experts not connected with the work said it was encouraging but that more research is needed to see how useful it would be for guiding patient care. One suggested that using a gene test along with PSA testing and other factors might help determine which men have enough risk of a life-threatening prostate cancer that they should get a biopsy. Many prostate cancers found early are slow-growing and won't be fatal, but there is no way to differentiate and many men have surgery they may not need.

Easton said the prospects for a genetic test are greater for prostate and breast cancer than ovarian cancer.

Breast cancer is the most common malignancy among women worldwide, with more than 1 million new cases a year. Prostate cancer is the second most common cancer in men after lung cancer, with about 900,000 new cases every year. Ovarian cancer accounts for about 4 per cent of all cancers diagnosed in women, causing about 225,000 cases worldwide.

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Scientists ID genetic markers tied to breast, prostate, ovarian cancer; no quick payoff seen

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