A NEW STRATEGY FOR EVALUATING THE IMPACT OF EPIDEMIOLOGIC RISK-FACTORS FOR CANCER WITH APPLICATION TO MELANOMA

A new stochastic framework is proposed for evaluating the individual a nd collective impact of cancer risk factors, and is applied to data on the incidence of melanoma. It is demonstrated that the standardized i ncidence ratio of second primary melanoma can be used to estimate the total coefficient of variation in risk in the population, subject to s ome simplifying assumptions. The coefficient of variation estimated in this manner thus can be used as a benchmark against which to judge th e contributions to this total variance of individual risk factors. A n onparametric estimator of the coefficient of variation attributable to a single risk factor on the basis of data from a case-control study i s derived, and its statistical properties are examined using simulatio ns. It is shown that the categorization of a continuous risk factor ca n attenuate the estimate substantially, and that estimation of the joi nt contribution of several risk factors will usually require statistic al modeling. Applying the methods to the epidemiology of melanoma, the results indicate that the known risk factors for melanoma explain onl y a relatively small fraction of the population variation in risk, in contrast to conventional views on this topic.