In recent years, more than 95 percent of U.S. women diagnosed with cancer at age 40 or younger got tested for mutations that raise their risk of future cancers, according to a new study.

The rate of genetic testing has steadily risen from about 70 percent in 2007, and that's a positive trend, researchers say, because the test results can influence women's decisions about treatment.

The National Comprehensive Cancer Network recommends that all women diagnosed with breast cancer at age 50 or younger get tested to see if they have BRCA gene mutations, which are known to raise the risk of breast and ovarian cancers, as well as the risk for recurrent cancers or later cancer in the opposite breast.

"The rates of testing in this population are probably higher than what you see in other populations, but it's still nice to see the improvement and more women having the opportunity to get tested," said senior author Dr. Ann H. Partridge of the Dana-Farber Cancer Institute in Boston

"We were surprised at how high the rates were over the time period," Partridge told Reuters Health by phone.

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The researchers analyzed data gathered between 2006 and 2014 in an ongoing study of young women with breast cancer. Partridge's team looked at almost 900 women age 40 and younger at 11 health centers across the country to see how many had been tested for BRCA mutations and whether test results had influenced their treatment.

Overall, 87 percent of the women said they had been screened for BRCA mutations within one year of their diagnosis. From 2007 onward, the proportion of women reporting testing increased each year, eventually including 96.6 percent of women diagnosed in 2012 and 95.3 percent of women diagnosed in 2013.

Among a total of 780 women tested during the study period, 59 did have what's known as a BRCA1 mutation and 35 reported having a BRCA2 mutation, while another 35 women said they had an indeterminate result or variant. The rest had no mutation.

Past research has found that women between ages 30 and 34 diagnosed with breast cancer and found to have the BRCA1 mutation have about a 1 in 3 chance of developing a new cancer in the next 10 years, the study team writes in JAMA Oncology. For women ages 35 to 39, the 10-year odds are about 1 in 4.

In the current analysis, almost 30 percent of women who were tested said knowledge of their genetic risk influenced their treatment decisions in some way.

About half of those who were tested and did not have mutations opted for a bilateral mastectomy to remove both breasts, compared to 86 percent of those who were mutation carriers. Mutation carriers were also more likely to have their ovaries removed.

Of the 117 women who were not tested for BRCA mutations within a year of diagnosis, almost a third said they had not discussed possible genetic mutations or screening with their doctor or a genetic counselor and 37 percent were thinking about future testing.

"We know we can reduce morbidity and mortality if we have the knowledge," and there are few to no downsides of BRCA testing for younger women with breast cancer, said Dr. Jeffrey N. Weitzel of City of Hope cancer center in Duarte, California, who coauthored an editorial alongside the new results.

BRCA testing was first commercially available in 1996, and in just 20 years its use has spread widely, Weitzel told Reuters Health.

"The recommendations are to test every woman with breast cancer under 40 for sure," Partridge said, but a small minority of women in this study said they were never told about testing or were told it was not necessary for them. "That's clearly the fault of the system and the provider leading that charge," she added.

More work can still be done to reduce barriers to testing, which may be higher for women who are uninsured, Partridge said.

"It wasn't until two years ago that Medicaid even covered this testing, the public health system hadn't really caught up," Weitzel said.

The study didn't include details on the nature of the genetic counseling offered to the patients, an important aspect of how they absorb and use the results of screening, he said.

"The more women who are tested, the critical thing is having the resources to support them with counseling," Partridge said.