Metastatic acral lentiginous melanoma in a tertiary referral center in Switzerland: a systematic analysis

Acral lentiginous melanoma (ALM) is a unique histopathological subtype of melanoma with a poorer prognosis than other cutaneous melanomas. This study aims to evaluate the clinicopathological characteristics, metastatic pattern, prognostic factors, response to systemic therapy, and overall survival (OS) of ALM in a White population. This is a retrospective study of patients who were diagnosed and/or treated for ALM at the Department of Dermatology of the University Hospital Zurich, Switzerland, from January 2005 to December 2015. Overall, 172 patients with histologically confirmed ALM were included in the study. In univariate Cox regression, Breslow thickness (P<0.001), age (P=0.003), status of sentinel lymph node (P=0.005), and ulceration (P=0.008) were identified as significant prognostic factors for OS in ALM. In multivariate analysis, only Breslow thickness (P=0.0003) showed statistical significance. The median OS (mOS) was 155.7 months in the entire cohort (n=172) and 11.2 months for stage IV patients (n=36), irrespective of treatment. When first treatment was considered (n=35), mOS for stage IV patients was 8.9, 16.6, 21.7, and 3.7 months, for patients who had received chemotherapy (ChT) (n=17), immunotherapy (n=9), targeted therapy (TT) (n=3), and no therapy (n=6), respectively. The overall response rate was 44% (7/16 patients) to ChT, 100% to TT (3/3), and 25% to ipilimumab (2/8). In our study, Breslow thickness represents the best prognostic factor for OS. In stage IV ALM patients treated with either immunotherapy or TT, there is a trend for extended mOS compared with ChT.