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

Abstract

Background: Tumor mitotic rate is a known prognostic variable in Stage I melanoma; however, its importance is unclear in Stages II and III.

Methods: Patients diagnosed with nonmetastatic cutaneous melanoma from 2010 to 2014 were identified from the National Cancer Institute's Surveillance, Epidemiology, and End Results registry.

Results: 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).

Conclusion: In this cohort study, tumor mitotic rate is an independent predictor of survival for localized melanoma.