Cancer Risks in A-T Heterozygotes

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Abstract
It is well established that ataxia-telangiectasia (A-T) patients suffer a grossly elevated risk of cancer, particularly lymphoma and leukaemia, but the possibility of an excess cancer risk of cancer in heterozygotes carriers of A-T mutations is more controversial. A number of studies indicate that female relatives of A-T patients suffer excess risk of breast cancer; based on an overview of all currently available data the estimated relative risk of breast cancer to A-T heterozygotes is 3·9-fold (95% CI 2·1–7·2). There is some suggestion that relative risk declines with age. In contrast, there is no consistent evidence of a risk from any other cancer; the estimated risk from all studies is 1·9 (95% CI 1·5–2·5) but some studies show a larger effect whilst others show no excess risk. On the basis of these results and the likely frequency of the A-T gene, A-T heterozygotes would account for between 1 and 13% of breast cancer cases, with 3·8% being the best estimate. However, unless the breast cancer risk has been seriously underestimated, the A-T gene will make little contribution to familial breast cancer.