Acral Melanoma in the Caucasian Population: A Comprehensive Cohort Study on Epidemiological, Clinicopathological, and Prognostic Features

Abstract

Acral melanoma; Cutaneous melanoma; Caucasian population

Melanoma acral; Melanoma cutáneo; Población caucásica

Melanoma acral; Melanoma cutani; Població caucàsica

Background: Acral melanoma is associated with poor prognosis. Studying the characteristics and prognosis of Caucasian patients is crucial to understand the distinct features of this tumor. Objectives: To analyze the epidemiological, clinicopathological, and prognostic features of acral melanoma in Caucasian patients. Methods: We conducted a retrospective, multicenter, cohort study of acral melanoma from a database across 20 hospitals from South Europe from January 2000 to December 2019. Results: A total of 733 acral melanomas were identified (median age, 67.5 years; 95.2%, Caucasians; 77.5% of which were located on the feet). Overall, 77.5% of cases were invasive melanomas. Foot melanomas had a higher proportion of invasive cases (80.8% vs 69.8%; p=0.003), stages III and IV at diagnosis (24.8% vs 11.7%; p<0.001), thicker Breslow depth (2.8mm vs 2.0mm; p=0.021) and a higher rate of positive sentinel lymph node biopsy (SLNB) (30.7% vs 15.7%; p=0.012). Thicker Breslow depth and later age of onset were risk factors for melanoma-specific survival. Thicker Breslow depth and ulceration were independent prognostic factors of relapse-free survival. Melanoma location and histopathological subtype were not associated with worse prognosis. Recurrences were a common finding (27.7%), with distant metastases appearing earlier than locoregional recurrences (1.32 years [IQR, 1.12-1.87] vs 2.14 years [IQR, 1.68-2.70]; p=0.015). Conclusion: This study, the largest in a predominantly Caucasian population, underscores the unfavorable outcomes of acral melanoma. Foot melanomas exhibited delayed detection, increased invasiveness, thicker Breslow depth, increased SLNB involvement, and higher AJCC stages. The high recurrence rate and early distant metastases emphasize the critical role of intensive follow-up and routine imaging modalities to detect asymptomatic relapses.

Melanoma research at Hospital Universitari Arnau de Vilanova of Lleida was supported by grants from ISCIII/FEDER ‘‘Una manera de hacer Europa’’ (PI18/00573 & PI21/00294 to R.M. Marti), CIBERONC-CB16/12/00231, and Generalitat de Catalunya (2021/SGR0093). The research at the Melanoma group in Hospital Clinic Barcelona is supported by the CIBER de Enfermedades Raras of the Instituto de Salud Carlos III, Spain; AGAUR 2017 SGR 1134 andCERCA Programme by Generalitat de Catalunya, Spain; a Research Grant from ‘‘Fundación Científica de la Asociación Espa˜ nola Contra el Cáncer’’ GCB15152978SOEN, Spain; European Commission under the sixth Framework Programme, Contract No. LSHC-CT-2006-018702 (GenoMEL), by the European Commission under the seventh Framework Programme, Diagnoptics; the European Commision under the HORIZON2020 Framework Programme, iTobos and Qualitop; and European Commission under the Horizon Europe Programme, HORIZON-MISS-2021-CANCER-02, MELCAYA (reference 101096667). This research was in part supported by grants from Fondo de Investigaciones Sanitarias P.I. 18/00419 and 22/01467 Spain. Part of the work was carried out at the Esther Koplowitz Center, Barcelona. J. Angel-Baldo held a predoctoral fellowship from IRBLleida/Diputació de Lleida.