The late effects study: design and subject representativeness of a Canadian, multi-centre study of late effects of childhood cancer.

The Late Effects Study of the Canadian Childhood Cancer Surveillance and Control Program was designed to assess psychosocial and physical health outcomes among survivors of childhood cancer compared to general population controls. The objectives of this paper are to describe the design and methodology of the multi-centre, retrospective cohort study, present clinical characteristics of the survivor population, and evaluate the representativeness of study controls. Response rates were 63% for surivors (n = 2,152) and 49% for controls (n = 2,432). Survivors with germ cell turmours and carcinomas were slightly under-represented among participants as were those who received more intense or multiple series of therapy. Study controls were similar to Census individuals based on marital and work status but did have a slightly higher level of education and income. Otherwise, no large or systematic differences were found. Thus, these long-term survivors and population controls can be validly studied to evaluate whether and to what extent survivors experience an excess of psychosocial or physical health problems compared to similarly aged Canadians who have never had cancer.