Men with advanced prostate cancer have much higher rates of mutations in some of the genes that repair DNA, a new study says — a finding that, in the future, could guide therapy options for such patients.
The study found that more than a tenth (11.8 per cent) of those surveyed with aggressive prostate cancer had mutations in at least one gene known to help repair DNA.
That rate is more than four times higher than those in the general population and more than twice the rate of men with localized prostate cancer. In the case of one DNA repair gene — BRCA2 — men with prostate cancer that had spread beyond the prostate were found to have 18 times the risk of carrying a mutation in that gene than men without prostate cancer.
"We were excited to learn how high the percentage of inherited DNA repair gene mutations is in men with metastatic prostate cancer because of the potential benefits of genetic testing," said Dr. Colin Pritchard, associate professor at the University of Washington's school of medicine, in a release. He is one of the authors of the study.
Mutations in some types of DNA repair genes are known to predispose people to several other types of cancer, such as breast cancer, ovarian cancer and pancreatic cancer. Because of that, the study's authors say these findings suggest that it may be a good idea for family members of those with aggressive prostate cancer who have inherited gene mutations to be offered genetic testing.
"It is ... important for family members as they may have inherited a gene that predisposes them to developing one of several types of cancer and heightened awareness could enhance early detection and treatment," said Dr. Peter Nelson of the Seattle-based Fred Hutchinson Cancer Research Center and an author of the study.
Nelson said the study's findings make a "compelling argument" for updating prostate cancer screening guidelines to include DNA testing "as a part of standard care for men with metastatic prostate cancer."
Oncologists say the implications of this study's findings are significant in that they might eventually lead to novel mutation-specific treatments for men with metastatic prostate cancer.
"It's a further step in the personalization of cancer treatment based on a specific mutation in an individual patient's cancer," said Dr. Robert Bristow, a professor of radiation oncology at the University of Toronto and an expert on prostate cancer at the Princess Margaret Cancer Centre.
"The defective DNA-repair in the cancer can be its Achilles heel as we can change treatment tactics and choose drugs that specifically target these unique defects," he told CBC News.
But Bristow cautions that more research is needed, pointing out that a day-to-day clinical test that could be used in hospitals has yet to be developed and clinical trials would be needed to assess whether any new treatments lead to a better outcome for patients. That could take several years.
The study, which pooled results from 692 men with aggressive prostate cancer, was published in Wednesday's New England Journal of Medicine.