Such counselling is important prior to undergoing genetic testing for mutations of BRCA, a gene strongly linked to the risk of both cancers, the study authors said.
And actress Angelina Jolie's revelations about discovering she had a BRCA mutation and deciding to have her breasts and ovaries removed has raised awareness about the importance of genetic tests and counselling.
In the study, patients who received genetic counselling beforehand displayed better knowledge of the process and possible results. And they reported more comfort heading into the test, according to the study results published online in the journal JAMA Oncology.
Not all experts agree
"While there certainly are physicians who are capable of providing appropriate genetics counselling for their patients, there are many who are not, and many who admit they don't feel comfortable trying to provide such counselling," said senior study author Dr Rebecca Sutphen.
She is president and chief medical officer of InformedDNA, a national provider network of genetics specialists.
Not all experts agree with the importance of genetic counselling prior to testing, however.
An accompanying editorial in the journal questioned the value of pretest counselling, arguing that the emphasis should be placed on genetic counselling for women who have received a positive test for BRCA mutations, so they fully understand their medical options.
"I think it's perfectly reasonable that the surgeon should order the test directly. I don't see that, in 2015, genetic counsellors add anything to the process," said editorial author Dr Steven Narod, director of the familial breast cancer research unit at the Women's College Research Institute in Toronto.
"If they have a mutation, they should see a genetic counsellor. If they don't, I think it just slows down the process."
Driven by profit
Narod also questioned the fact that the study was funded by the health insurer Aetna and conducted by researchers affiliated with InformedDNA.
"This is a paper driven by a for-profit company that sells genetic counselling services," he said.
About 55 percent to 65 percent of women who inherit a harmful BRCA1 mutation and about 45 percent of women who inherit a harmful BRCA2 mutation will develop breast cancer by age 70, compared with just 12 percent of all women, according to the U.S. National Cancer Institute (NCI).
In addition, about 39 percent of women with BRCA1 mutations and 17 percent of women with BRCA2 mutations will develop ovarian cancer by 70, compared with 1.3 percent of all women, the NCI says.
BRCA mutations have been so strongly established as a cancer risk factor that the U.S. Preventive Services Task Force has added BRCA risk assessment and genetic counselling to its list of recommended preventive procedures. That means insurers compliant with the Affordable Care Act must pay the full cost of providing such counselling and testing if a woman has a family history of breast or ovarian cancer.
In collaboration with Aetna, researchers surveyed nearly 3,900 women whose doctors ordered BRCA testing between December 2011 and December 2012.
Slightly less than half of the women who underwent BRCA testing had a family history of breast or ovarian cancer, while slightly more than half had no personal history of breast or ovarian cancer, the researchers found.
Of those women, about 37 percent reported receiving genetics counselling from a genetics professional prior to testing, the study authors said. The most common reason reported by women for not receiving this service was the lack of a recommendation from their doctor.
The women who did receive genetic counselling by a trained genetics professional displayed greater knowledge of BRCA and expressed greater understanding and satisfaction, according to the results.
Dr Mary Daly, chair of clinical genetics at Fox Chase Cancer Centre in Philadelphia, called the low rate of genetic counselling "concerning".
A cost-saving measure
Such counselling is important to help a woman understand the implications of the test, especially since the falling cost of genetic testing means that doctors often order a test that covers dozens of genes.
"We're no longer just doing a test for BRCA. We're doing a panel of up to 25 different genes," Daly said. "That makes the interpretation of the results that much more difficult."
But only one out of every 20 women in this study came back positive for a BRCA mutation, which raises the question of whether the other 19 women received any benefit at all from the counselling they got beforehand, Narod said.
In the past, insurance companies required genetic counselling prior to testing as a cost-saving measure, to make sure that women without a family history of cancer were steered away from the then-expensive procedure, Narod said.
Women would be better served if the limited number of genetics counsellors in the United States focused on helping them interpret the results of a positive test, rather than preparing them prior to the test, he said.
Women with a positive test might need to have their breasts or ovaries removed as a cancer prevention measure, or might have to undergo regular MRI screenings for cancer, Narod said. They also face passing along this knowledge of hereditary cancer risk to other female family members.
By comparison, there's no real genetic counselling required if the test comes back negative.
"The doctors are perfectly capable of ordering the test, providing the preliminary information the patient needs in order to decide whether to have the test, and interpreting a negative test," Narod said.
"The genetic counsellor should focus on interpreting a positive test."
Image: Doctor and patient from iStock