Prognostic impact of Breslow thickness in acral melanoma: A retrospective analysis

Background: Evidence for the prognostic importance of tumor thickness in acral melanoma (AM) patients is limited. Objective: The objective of the study was to determine the prognostic impact of Breslow thickness in AM. Methods: This multicenter study enrolled patients diagnosed with localized AM between January 1, 2000 and December 31, 2017. Melanoma-specific survival (MSS) in different tumor thickness strata (T1-T4: ≤1, >1-2, >2-4, >4 mm, respectively) was estimated by the Kaplan-Meier method. Comparisons were performed by the log-rank test and multivariable Cox regression. Results: A total of 853 patients with clinical N0 (cN0) AM were included in the analysis. The median follow-up time was 60.1 months. The median MSS in patients with T1-T4 disease was not reached, 111.0, 92.8, and 67.1 months, respectively. MSS differed significantly among cN0 patients with T1-T3 AM (log-rank P = .004,. 012, <0.001 for T1 vs T2, T2 vs T3, and T1 vs T3, respectively); however, there was no significant difference between T3 and T4 AM (hazard ratio = 0.82, 95% CI, 0.62-1.09). Six-subgroup analyses confirmed that survival outcomes were similar between different subgroups with tumor thickness >2 mm. Limitations: The limitations were retrospective design and some missing variables. Conclusions: There was no association between tumor thickness and survival in AM patients with a Breslow thickness >2 mm.