The progressive relationship between increasing Breslow thickness and decreasing survival is lost in patients with ultrathick melanomas (≥15 mm in thickness).

BACKGROUND:Survival tends to decrease as the Breslow thickness of a primary melanoma increases. However, little is known about the prognostic value of Breslow thickness in patients with very thick melanomas. OBJECTIVE:We sought to assess survival in patients with melanomas ≥4.0 mm in Breslow thickness. METHODS:A pooled cohort of 5595 patients (4107 Dutch and 1488 Australian) with melanomas ≥4.0 mm in thickness diagnosed from 2000 to 2014 was analyzed. Standard and spline Cox regressions were generated for overall survival (OS) and recurrence-free survival (RFS). RESULTS:The median follow-up was 3.4 years. The continuous hazard ratios (HRs) for OS and RFS increased steadily as the Breslow thickness increased to 15 mm, stabilized up to 20 mm, and decreased thereafter. Using patients with melanomas 4 to <10 mm thick as a reference group, the categoric HR for OS increased up to the 15- to -<20-mm thickness category and then decreased (HR, 1.46 [95% CI, 1.29-1.66], P < .0001 for 10-<15 mm; HR, 1.97 [95% CI, 1.55-2.51], P < .0001 for 15-<20 mm; and HR, 1.36 [95% CI, 1.07-1.84], P = .045 for ≥20 mm). For the RFS, similar trends were observed. LIMITATIONS:Retrospective study. Small cohorts of patients with melanomas 15-<20mm and ≥20mm. CONCLUSION:The progressive relationship between increasing Breslow thickness and decreasing survival is lost in patients with melanomas ≥15 mm in thickness.