To the Editor.—
In the article by Li and Fraumeni entitled "Prospective Study of a Family Cancer Syndrome" (1982;247:2692), it was stated that 70% of the individuals in four kindreds were affected with the development of cancer. This proportion is higher than that expected on the basis of an autosomal dominant mechanism. A previously reported study demonstrated a 50% risk, which is consistent with the hypothesis of essentially complete penetrance of a dominant gene.1The difference between the observed rate and the expected rate is an artifact in calculation. A proper segregation analysis that corrects for the bias of ascertainment is necessary in this instance. The kindreds include sibships with only one member, which inflates the number affected. Individuals in the direct line of ascent from the proband have the same effect. It has been shown that the most appropriate procedure is to discard the probands as well as
Harris DJ. Family Cancer Syndrome. JAMA. 1982;248(16):1972. doi:10.1001/jama.1982.03330160024008
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