Prognostic index for malignant melanoma

Abstract

This report verifies the ability of a Prognostic Index (PI) to accurately predict 5-year survival rates for 879 Stage I cutaneous malignant melanoma (MM) patients seen at New York University Medical Center. The PI used in this study was first reported from Munich, West Germany, and is calculated from standard histologic sections by multiplying the MM thickness in millimeters (Breslow method) by the number of MM mitoses per square millimeter. A PI value of less than 19 versus greater than or equal to 19 was found to be a significant and independent prognostic variable for Stage I MM when compared with seven other predictive variables (including Breslow thickness). These PI intervals identified a subgroup of patients with MM of intermediate thicknesses (1.50-3.49 mm) whose significantly worse survival would not have been anticipated if prognosis were determined by Breslow thickness alone. For example, patients with MM 1.50 to 2.49 mm thick have a 5-year survival rate of 84.1% determined by Breslow thickness alone; however, among these patients exists a subgroup with PI greater than or equal to 19 whose survival rate is only 57.6%. This study verifies the additive usefulness of the PI in predicting survival rates of patients with Stage I cutaneous MM.