Abstract
Background/Objectives: Acral melanoma is associated with poor postoperative outcomes, yet evidence supporting adjuvant treatment in this subtype remains limited. Vaccine-based immunotherapy has shown promising efficacy as adjuvant treatment for high-risk melanoma. We evaluated associations of adjuvant dendritic cell (DC) vaccine–based cellular immunotherapy plus high-dose interferon-α2b (HD-IFN) with recurrence-free survival (RFS), overall survival (OS), and safety in resected high-risk acral melanoma.
Methods: This single-center retrospective cohort included 438 patients with resected stage IIB–IIID acral melanoma treated during 2012–2016; 162 received DC vaccine–based cellular immunotherapy plus HD-IFN and 276 received HD-IFN alone. Surgery was the time origin, and DC initiation was modeled as a time-dependent exposure. Multivariable Cox models adjusted for prespecified baseline covariates.
Results: Median follow-up was 103.4 months. The primary complete-case analysis included 426 patients, with 352 RFS events and 267 deaths. DC exposure was associated with RFS (summary hazard ratio [HR], 0.614; 95% confidence interval (CI), 0.489–0.772; p < 0.001), whereas no clear OS association was observed (HR, 0.984; 95% CI, 0.758–1.277; p = 0.904). Sensitivity analyses yielded similar conclusions. Because proportional-hazards assumptions were violated, HRs were interpreted as summary associations over follow-up. Grade ≥3 treatment-related adverse events occurred in 16.0% and 10.5% of patients, respectively; no treatment-related deaths occurred.
Conclusions: In this historical cohort, DC vaccine–based cellular immunotherapy was associated with RFS after accounting for treatment initiation and measured baseline confounding, without a clear OS association. Residual confounding, nonproportional hazards, and the historical HD-IFN comparator warrant cautious interpretation.