Abstract
Patients with heritable cancer syndromes often develop multiple primary cancers (mpc) affecting one or more organs or tissues. However, it is less clear whether the presence of mpc in a patient implies that genetic factors have an important role in aetiology. We have investigated this by comparing the surname distributions of 11205 males with mpc on the Scottish Cancer Register, with corresponding distributions in male controls and in males with individual cancers, by calculating coefficients of relationship by isonymy. Our results suggest that although genetic factors may have a role in the aetiology of mpc, particularly if the cancers affect different tissues or organs, their effect is small compared with that of environmental factors.