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22 July 2008
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Family history not a predictor of early onset breast cancer
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MedWire News: A family history of breast cancer is not a useful indictor as to whether a woman will develop breast cancer herself at an early age, study results suggest.
The researchers say that applying such criteria as the basis for early intensive mammography screening is not an effective strategy and may actually cause unnecessary worry and psychological harm.
Many studies have demonstrated that the relatives of breast cancer patients face an increased risk for developing the disease themselves, Geertruida de Bock (Groningen University Medical Center, The Netherlands) and colleagues note.
Indeed, the demand for referring healthy women with a family history of breast cancer for intensive screening or genetic testing is rising.
In most guidelines, the criteria for starting breast cancer surveillance before the age of 50 years is at least one first-degree relative diagnosed with breast cancer under the age of 40 or 50 years, with additional criteria including more than one relative with breast cancer, relatives with bilateral breast cancer, ovarian cancer, male breast cancer, or prostate cancer.
The problem is that these criteria have been derived from estimates based on data from cancer-prone families or from BRCA1/2 mutation families.
The researchers explain: "As BRCA1/2 mutations explain only a small proportion of the familial clustering of breast cancer, estimates based on these high-risk families may thus have limited value for the prediction of the age of onset of breast cancer in the general population."
In the current study, de Bock et al investigated the incidence of breast, prostate, and cervical cancers in the first- and second-degree relatives of 1987 women, 136 (6.8%) of whom subsequently developed breast cancer themselves.
The risk for being diagnosed with breast cancer aged 30 years or younger was increased when there were: (1) at least 2 cases of female breast cancer in first-degree relatives (yes/no; hazard ratio [HR]=3.09); (2) at least 2 cases of female breast cancer in first or second-degree relatives under the age of 50 (HR=3.36); (3) at least 1 case of female breast cancer under the age of 40 in a first- or second-degree relative (HR=2.06); and (4) any case of bilateral breast cancer (HR=3.47).
However, due to the low overall prevalence of early breast cancer in the population, the positive predictive value of the presence of at least 2 of the 4 above criteria was 13% for breast cancer before the age of 70, 11% for breast cancer before the age of 50, and just 1% for breast cancer before the age of 30.
Based on their findings, de Bock et al call for a revision of current guidelines regarding familial breast cancer and screening and say that the four criteria identified in their study could be used to "reassure a large number of women regarding their personal breast cancer risk at an early age."
The research is published in the online journal BMC Breast Cancer.
BMC Cancer 2008; Advance online publication
http://www.biomedcentral.com/bmccancer/
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