CLINICAL AND HISTOPATHOLOGIC PREDICTORS OF SURVIVAL IN PATIENTS WITH MALIGNANT-MELANOMA - A POPULATION-BASED STUDY IN SWEDEN

Background: Previous malignant melanoma studies regarding prognostic f actors have often selected their patients from hospitals. Unfortunatel y, most of these studies have had small numbers of patients, consisted of short-term data sets, omitted important factors, did not optimize histopathologic classification, had too short or inadequate follow-up, and did not test their predictive models. Purpose: Our study goals we re to identify independent clinical and histopathologic determinants o f survival in malignant melanoma, to analyze changes in prognostic val ue over follow-up time, and, finally to construct a prognostic index. Methods: A random sample from the Swedish Cancer Registry of the recor ds of 498 (246 men and 252 women) patients defined by gender, five 5-y ear time periods of diagnosis from 1960 through 1984, and five anatomi c sites formed the cohort on whom data were analyzed by univariate ana lyses. Multivariate analyses were based on data on 476 patients with c omplete information about all variables. All patients in the cohort ha d complete follow-up through December 31, 1989. Clinical information w as abstracted and recorded as: date of diagnosis, stage at diagnosis, sex, age, anatomic site of primary tumor, date of death, and cause of death. Histopathologic slides were re-examined and classified with reg ard to histogenetic type, level of invasion, tumor thickness, ulcerati on, vascular invasion, regression, lymphocytic reaction, pre-existing nevus, and cell type. Results: All variables, except pre-existing nevu s and cell type, were significant predictors of survival. In the multi variate analyses including all variables, women still had a significan t, 33% lower relative hazard than men. The prognosis was poor in the y oungest age group. Patients with external ear, scalp-neck, and trunk-l ocated melanoma had increasing relative hazard when all variables were included. Regional metastases and tumor thickness remained independen t prognostic factors. No significant association between histogenetic type or level of invasion persisted. Patients whose tumors showed ulce ration or vascular invasion had lower relative hazard when all variabl es were included. Level of invasion, tumor thickness, ulceration, and vascular invasion were significantly associated with the prognosis dur ing both short- and long-term follow-up. The patients were subgrouped according to percentage fractions of their score on the prognostic ind ex. Survival curves for these groups of patients were well separated, thus identifying patients with a low or high risk of death from malign ant melanoma. Conclusion: The present population-based study identifie s independent clinical and histopathologic predictors of survival in c utaneous malignant melanoma and emphasizes the role of histopathologic characteristics such as tumor thickness, ulceration, and vascular inv asion besides anatomic site.