Mitotic rate correlates with sentinel lymph node status and outcome in cutaneous melanoma greater than 1 millimeter in thickness: A multi-institutional study of 1524 cases.

Abstract

The 7th edition of the TNM American Joint Committee on Cancer classification incorporates mitotic rate (MR) only for primary cutaneous melanoma (PCM) with Breslow thickness (BT) ≤1 mm. To investigate whether and to what extent MR is able to predict sentinel lymph node (SLN) status and clinical outcome of PCM patients with BT >1 mm. The study included consecutive patients with PCM. Logistic regression and Cox regression model were used to analyze the impact of MR on SLN status, disease-free survival (DFS), and overall survival. From 1998 to 2015, 1524 PCM (median age 57.8 years) cases were diagnosed with a BT >1 mm in six centers of the Italian Melanoma Intergroup. Median follow-up was 5.0 years. By multivariate analysis, MR was associated with SLN positivity (odds ratio 1.98, 95% confidence interval [CI] 1.12-3.50, P = .018). After adjusting for BT, ulceration, age, sex, and SLN status, MR correlated with a poor DFS (hazard ratio 1.52, 95% CI 1.18-1.97, P = .002) and overall survival (hazard ratio 1.63, 95% CI 1.17-2.29, P = .004). Retrospective analysis. MR is an independent prognostic factor for PCM patients with BT >1 mm. Incorporating this tissue biomarker could provide a better stratification of patients entering clinical trials in the adjuvant setting.