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Family history criteria may not be specific enough to identify women in the general population who would benefit from early breast cancer screening, according to a new study.

Family history criteria may not be specific enough to identify women in the general population who would benefit from early breast cancer screening, according to a new study.

"Breast cancer is very common. Familial clustering is also rather common," Dr. Geertruida H. de Bock, the study's first author, told Reuters Health. "About 25 per cent to 30 per cent of breast cancer is family clustered, but the incidence of breast cancer in the family is not very useful in predicting if you will get breast cancer yourself."

At present, having a first-degree relative diagnosed with breast cancer before age 40 is considered to be an indication for starting breast cancer surveillance before age 50, Dr. de Bock and her team note in their report, but this practice is based on estimates from families with BRCA1/2 mutations or who are otherwise cancer-prone.

To better understand the risk in the general population, the researchers looked at 1,987 women, all of whom had sisters who had been diagnosed with breast cancer. Their findings appear in the BioMed Central journal BMC Cancer, published online on July 22.

The researchers identified four familial factors that were related to developing breast cancer at a younger age:

• At least two cases of breast cancer in first-degree relatives;
• At least two cases of female breast cancer in first or second-degree relatives younger than 50;
• At least one case of breast cancer in a first or second-degree relative younger than 40;
• Or any case of bilateral breast cancer.

Women who had at least two of these risk factors were 10.62 times more likely than those with no risk factors to develop breast cancer by age 30. Hazard ratios dropped with age, to 4.56 by age 40 and 1.96 by age 50.

Due to the low prevalence of breast cancer in younger patients, however, the positive predictive value of having two or more of the above factors was 13 per cent for breast cancer diagnosed before age 70, 11 per cent for a diagnosis before age 50, and one per cent for a diagnosis before age 30, with negative predictive values of 94 per cent, 97 per cent, and almost 100 per cent, respectively.

Therefore, the researchers say, women with just one of the familial factors may not need early breast cancer screening.

If the model were used in clinical decision-making, "it would be an easy-to-use method to reassure a large number of women regarding their personal breast cancer risk at an early age and their need to be referred to early screening programs or genetic centers," the investigators conclude.

"There is a tendency to screen everyone and I think screening has disadvantages as well as advantages," Dr. de Bock said. "You should be critical about it and really think about it if there isn't really an increased risk."

BMC Cancer 2008