July 22, 2008 -- Family history is a much poorer predictor of early breast cancer risk than most women realize, say researchers whose latest study argues against using family history alone to determine a young woman's risk for the disease.
When they examined the predictive value of family history for assessing breast cancer risk early in life, researchers from Leiden University Medical Center in the Netherlands found little correlation between family history and breast cancer incidence at a population level.
A predictive model developed by the researchers found that roughly one in 10 women with a strong family history of the disease could be expected to develop breast cancer before the age of 50 and just one in 100 would develop the disease before their 30th birthday.
The findings suggest that too many women may be undergoing genetic testing and close surveillance for breast cancer based on family history, the researchers say.
"Applying family history related criteria results in the screening of many women who will not develop breast cancer at an early age," epidemiologist Geertruida H. de Bock and colleagues write in the latest issue of BMC Cancer.
Family History of Breast Cancer
According to the American Cancer Society, a family history of breast cancer does increase a woman's risk of breast cancer. This risk is higher in women whose close relatives (maternal and paternal relatives) have the disease. Having a mother, sister, or daughter with breast cancer approximately doubles a woman's risk, even though 70% to 80% of women with breast cancer do not have a family history.
A family history of breast cancer is not the same as breast cancer risk associated with the inherited mutations of BRCA1 or BRCA2 genes.
In an effort to better understand the predictive value of family breast cancer history, de Bock analyzed its impact in close to 2,000 women with and without breast cancer.
Breast cancer risk was assessed based on four accepted indicators of family risk:
Having at least two female first-degree relatives (sister, mother, or daughter) with breast cancer.
Having at least two female relatives -- either first- or second-degree -- diagnosed with breast cancer before the age of 50. Second-degree relatives include grandmothers, aunts, and nieces.
Having at least one female first- or second-degree relative diagnosed before the age of 40.
Having a relative with a diagnosis of breast cancer in both breasts.
Women with only one first-degree relative diagnosed with breast cancer before the age of 50 were not found to be at increased risk for developing breast cancer early in life.
The researchers concluded that women with none of these family risk factors or just one of them had a very small risk of developing breast cancer early in life and would probably not benefit from genetic testing or intensive early screening.
At the population level, risk was still relatively low for women with two or more family risk indicators.
"Due to the low prevalence of early breast cancer in the population, the predictive value of family history of breast cancer was 13% before the age of 70, 11% before the age of 50, and 1% before the age of 30," de Bock notes in a press statement.