Tumor mitotic rate is an independent predictor of survival for nonmetastatic melanoma

Tumor mitotic rate is a known prognostic variable in Stage I melanoma; however, its importance is unclear in Stages II and III. Patients diagnosed with nonmetastatic cutaneous melanoma from 2010 to 2014 were identified from the National Cancer Institute's Surveillance, Epidemiology, and End Results registry. Of a total of 71,235 patients, the majority were white (94.7%), male (58.5%), and had a Stage I tumor (79.0%). On univariable analysis, 5-year disease-specific survival decreased with each increasing tumor mitotic rate category of 0–3, 4–10, and >10 mitoses/mm2 (Stage I 98.3%, 90.9%, 79.7%; Stage II 86.1%, 74.2%, 72.9%; and Stage III 72.5%, 58.6%, 49.7%). In multivariable models, tumor mitotic rate as both a continuous and categorical variable was associated with disease-specific survival for Stages I–III melanoma. Each unit increase in tumor mitotic rate increased the risk of death by 23% in Stage I, 5% in Stage II, and 3% in Stage III. Compared with the 0–3 tumor mitotic rate category, the risk of disease-specific mortality increased for tumors in the 4–10 and >10 categories for Stage I (RR 3.07 and 6.74, P < .0001), Stage II (RR 1.37 and 1.62, P = .0002), and Stage III (RR 1.24 and 1.35, P = .0004). In this cohort study, tumor mitotic rate is an independent predictor of survival for localized melanoma.