Women in Study Acted on Positive DNA Test

More than half of women who tested positive for a genetic predisposition to breast or ovarian cancer opted to have their healthy breasts or ovaries removed to head off the disease, a new study shows.

A DNA test has been available since 1994 to determine whether women have genetic mutations linked to the cancers, but the Dutch research is the first to track how many women took it and how many chose preemptive surgery.

Nearly half of women in the study, all at high risk for the two cancers, chose to take the DNA test, according to the research published last week in the Lancet medical journal (https://www.thelancet.com).

Young women with children were more likely than older women to take the tests and to have mastectomies once they discovered they had the mutations.

Dr. Lynn Hartmann, a cancer specialist at the Mayo Clinic in Rochester, Minn., who has conducted similar research but was not connected to the study, said it provides important new information.

“There have been people who say [surgery] . . . is selected by only 5% of women,” Hartmann said. “That’s based on their own opinion and that’s just not good enough. You need the actual numbers.”

The study involved 411 cancer-free women with one or more relatives with one of two genes linked to breast and ovarian cancers. It found that 48% of the women took the opportunity to find out if they carried the genetic mutation.

When the tests revealed they had a mutation, 51% chose a double mastectomy and 64% opted to have their ovaries removed.

Experts estimate that 1 in 400 women has a mutation of one of the two genes, known as BRCA1 and BRCA2. Those women can have an 85% risk of developing breast cancer and a 65% chance of getting ovarian cancer.

“A lot of women with gene mutations feel their breasts are time bombs,” said the study’s lead researcher, Dr. Jan Klijn at Erasmus University in Rotterdam, the Netherlands.

The study results, which Klijn presented at a U.S. cancer conference last month, showed that of the 70 women who had their breasts removed, none developed cancer in the following six years. An earlier study by Hartmann at the Mayo Clinic showed the surgery slashed the risk of breast cancer by 90%.

Dr. Henry Lynch, a professor of medicine at Creighton University in Omaha, Neb., who has conducted similar research, said the demand for preemptive mastectomy has increased over the last decade in the United States.

Lynch said his findings, to be presented at a conference this month, are almost identical to those of the Dutch study.

Dr. James Mackay, a cancer genetics expert at the Cancer Research Campaign in Addenbrokes Hospital in Cambridge, England, said that while more women may opt for mastectomy in the near future, preventive hormonal treatments now being developed may be a better option in the long term.

“The knife has never been the real answer to the treatment of breast cancer,” he said.

Studies of preventive drug treatment may show that women can protect themselves against breast cancer and still keep their breasts, he said.