NEW FINDINGS
• For breast cancer, researchers calculated that by using all known markers, including the new ones, they could identify 5 percent of the female population with twice the average risk of disease, and 1 percent with a three-fold risk. The average lifetime risk of getting breast cancer is about 12 percent in developed countries. It’s lower in the developing world where other diseases are a bigger problem.
• For prostate cancer, using all the known markers could identify 1 percent of men with nearly five times the average risk, the researchers computed. In developed countries, a man’s average lifetime risk for the disease is about 14 to 16 percent, lower in developing nations.
• Markers can also make a difference in estimates of breast cancer risk for women with the BRCA1 or BRCA2 gene mutations. Such women are rare, but their lifetime risk can run as high as 85 percent. Researchers said that with the new biomarkers, it might be possible to identify the small group of these women with a risk of 28 percent or less.
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 helpfurther reveal a person’s risk for breast, ovarian or prostate cancer, scientists reported Wednesday.
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 that funded much of the research.
One analysis suggests that among men whose family history gives them roughly a 20 percent lifetime risk for prostate cancer, such genetic markers could identify those whose real risk is 60 percent.
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 percent from women whose risk is about 20 to 50 percent. 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.
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.
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 percent of all cancers diagnosed in women, causing about 225,000 cases worldwide.
The new results were released in 13 reports in Nature Genetics, PLOS Genetics and other journals. They come from a collaboration involving more than 130 institutions in the United States, Europe, and elsewhere. The research was mainly paid for by Cancer Research U.K., the European Union and the U.S. National Institutes of Health.
Scientists used scans of DNA from more than 200,000 people to seek the markers, tiny variations in the 3 billion “letters” of the DNA code that are associated with disease risk.
The scientists found 49 new risk markers for breast cancer plus a couple of others that modify breast cancer risk from rare mutated genes, 26 for prostate cancer and eight for ovarian cancer. Individually, each marker has only a slight impact on risk estimation, too small to be useful on its own, Easton said. They would be combined and added to previously known markers to help reveal a person’s risk, he said.
About the Author
