Screening for mutations in a gene known as CHEK2 may help determine a woman's odds of breast cancer if the disease runs in her family, Polish scientists suggested.
A woman harbouring a CHEK2 mutation, for instance, would have a 34% risk of developing breast cancer if her mother or sister had the disease, they estimate.
But US experts said the test isn't ready for prime time yet, and emphasised that Polish women might be different from Americans.
"It would be premature to tell women that they should all go out and get CHEK2 screening," said Dr James P. Evans, editor-in-chief of the American College of Medical Genetics' journal Genetics in Medicine.
Finding an important breakthrough
Still, he called the study a nice start.
Women with a suspicious pattern of breast or ovarian cancer in the family are already encouraged to get screened for mutations in the BRCA 1 and 2 genes that warn of a heightened tumour risk.
But if those tests come up empty, doctors don't have much to offer, Dr Diana Petitti, of the Arizona State University in Phoenix, told Reuters Health.
"This does represent an important breakthrough," she said of the new findings. "But this is a field where replication is critical."
Breast cancer runs in the family
The Polish researchers tested the genes of nearly 7,500 women with breast cancer who didn't have BRCA 1 mutations.
They found that 3% had a certain type of mutation in the CHEK2 gene. Among women without breast cancer, less than 1% harboured mutations.
Although CHEK2 has been tied to cancer before, it wasn't clear what role cancer in the family played. When the team asked the women whether they had any affected relatives, those whose mother or sister had had breast cancer were at highest risk.
About one in eight American women - or some 12% - will get breast cancer at some point in their lives.
Tests readily available
In Poland, that figure is only 6%, Dr Cezary Cybulski of the Pomeranian Medical University in Szczecin and colleagues write in the Journal of Clinical Oncology.
From their findings, they estimate that a woman with a CHEK2 mutation has a risk of 20%. If she also has a mother or sister with breast cancer, her risk jumps to 34%, and to 44% if a second-degree relative is also sick.
"CHEK2 mutation screening detects a clinically meaningful risk of breast cancer and should be considered in all women with a family history of breast cancer," the researchers say.
According to Evans of the American College of Medical Genetics, such tests are already available, likely for less than R600. While that may sound cheap, it adds up quickly, he added.
"If we give this test to all women who have a close relative with breast cancer, you are now talking about a huge expenditure," Evans told Reuters Health.
At this point, he said, women with a family history of breast cancer would be better off talking to their doctor, or a genetic counsellor, to find out what options they have.
Those who have BRCA 1/2 mutations, for instance, may consider having their breasts and ovaries removed, or taking certain medications, to stave off tumours.
Petitti also struck a cautious note about the new test.
"We are just not there yet," she said. "It's a matter of research at this point."
(Reuters Health, August 2011)
BRCA 1 and 2