Background: Several authors have proposed the use of patients with double primary
malignancies affecting the same or contralateral organ as a genetically enriched resource of
cases for epidemiologic case–control studies in cancer. Such an approach is based on the
assumption that the factors that increase the risk of a second primary are the same ones
which influence the risk of a first primary. The advantages for statistical power are premised
on the assumption that relative risks in survivors of a first primary cancer are similar to …