CURED FRACTION AND SURVIVAL-TIME AS FUNCTIONS OF THICKNESS, SITE, HISTOLOGIC TYPE, AGE, AND SEX

Background. Previously, nonparametric or semiparametric methods have b een used to determine the relationship of various prognostic covariate s with survival of skin cancer. Unfortunately, these methods do not re adily distinguish between factors that modulate cure and those that mo dulate survival time among uncured patients. Methods. The multivariate lognormal model can be used to detect the association of cured fracti on and median survival time with specific prognostic covariates. This model was applied to survival data from 2004 patients with skin melano ma using the following prognostic covariates: thickness, site, and his tologic type of the tumor and sex and age of the patient. Results. Thi s analysis revealed that a low cured fraction was associated with thic k lesions and location other than trunk or extremity, whereas a short median survival time was associated with thick lesions and tumor locat ed on the trunk. Advanced age was highly associated only with short me dian survival time. Conclusion. The lognormal survival model offers in sight into the biology of skin melanoma by distinguishing the roles pl ayed by likelihood of cure and survival time. The differential associa tions of various covariates with these two parameters suggest that bio logic mechanisms that govern cure are not identical to those that gove rn survival time.