Coefficients of relationship by isonymy among oral cancer registrations in Scottish males.

The role of inherited susceptibility to oral cancers was studied by comparing groups of cancer patients and controls in terms of the coefficient of relationship by isonymy (Ri), both within and between Regions of mainland Scotland. Surname distributions for 3658 male cancer cases were derived from the Scottish Cancer Register for the years 1959-85. Control distributions were derived from a total of 32,468 male deaths in Scotland for 1976. For cancer of the floor of mouth, there was no evidence for increased isonymy in patients compared to controls and therefore no indication that familial factors contribute to cancer at this site. For cancer of the tongue there was a suggestion of increased isonymy within but not between Regions, perhaps reflecting environmental risk factors common to members of the same family. For cancers of the lip and salivary gland there was evidence of increased isonymy both within and to a lesser extent between Regions, suggesting a genetic contribution. There is corroborative evidence from other sources for a heritable component in salivary gland cancer but the reasons for the similar pattern of results in cancer of the lip are less clear.