Prospective validation of molecular prognostic markers in cutaneous melanoma: A correlative analysis of E1690

Abstract

Purpose: To validate the prognostic impact of combined expression levels of three markers (SPP1, RGS1, and NCOA3) in melanoma specimens from patients enrolled in the E1690 clinical trial of high-dose or low-dose IFNa-2b versus observation. Experimental Design: Tissue was available from 248 patients. Marker expression was determined by digital imaging of immu-nohistochemically stained slides. The prognostic impact of each marker was first assessed by recording its expression value relative to the median. A multimarker index was then developed to combine marker expression levels by counting for each patient the number of markers with high expression. The impact of the multimarker index on relapse-free survival (RFS) and overall survival (OS) was assessed using Kaplan–Meier analysis, and both univariate and multivariate Cox regression analyses. Results: By Kaplan–Meier analysis, high multimarker expression scores were significantly predictive of RFS (P < 0.001) and OS (P < 0.001). Stepwise multivariate Cox regression analysis with backward elimination that included routine clinical and histo-logic prognostic factors revealed high multimarker expression scores and tumor thickness as the only factors significantly and independently predicting RFS and OS. Stepwise multivariate Cox regression analyses that also included treatment type and number of positive lymph nodes generated identical results for both RFS and OS. In the molecularly defined low-risk subgroup, patients treated with high-dose IFN had a significantly improved RFS compared with patients in the other two subgroups (P < 0.05). Conclusions: These results validate the independent impact of combined expression levels of SPP1, RGS1, and NCOA3 on survival of melanoma in a prospectively collected cohort.