Current methods of predicting a woman’s inherited breast cancer risk do not account for smaller families and may leave some women unaware of their risk for future cancers, US researchers have claimed.
“You’ve got to have family to have a family history of breast cancer,” said Dr Jeffrey Weitzel of the City of Hope cancer center in Duarte, California.
Weitzel said women with breast cancer are often asked if they have a family history of the disease. Their answers are used to gauge whether referral for genetic testing is warranted.
“Most of the models used to determine who might get genetic testing were based on large families and families where there were multiple cases,” he said.
“But what about those women who were younger than expected when they got their cancer but who don’t have a family history of cancer?”
The study appears in the Journal of the American Medical Association.
While between 5 to 10% of breast cancer cases are inherited, women with mutations of the BRCA1 or BRCA2 gene have an up to 70% higher risk of developing another breast or ovarian cancer.
To analyse whether risk assessment tools were underestimating the risk of some patients, Weitzel and colleagues, between 1997 and 2007, evaluated 306 women who had breast cancer before age 50.
Women with fewer than two close female relatives on either parent’s side who lived past the age of 45 were considered to have a limited family structure. About half of patients fell into this group.
The study found that participants with less family information to draw from actually had a higher risk of having the BRCA gene mutation than those with larger families.
BRCA gene mutations were found in 13.7% of participants with limited family structure, compared with 5.2% with adequate family structure.
Weitzel said the findings challenge the accuracy of the probability models used to guage the need for genetic tests.
“Finding out if someone is at inherited risk clearly does change how we follow people,” said Dr Noah Kauff of Memorial Sloan-Kettering Cancer Center in New York, who wrote an accompanying editorial advising doctors to use these risk models with caution.
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