Long-term outcomes after amputation and sentinel node biopsy for subungual melanoma: A single-institution series

Background: Subungual melanoma (SUM) is a rare tumor with historically poor outcomes. Thus, the benefit of proximal versus distal amputation in SUM remains unclear. Methods: We performed a retrospective review of our prospectively-maintained institutional melanoma database, including SUM and non-subungual acral melanoma (AM) patients who underwent sentinel lymph node biopsy (SLNB) between 1999 and 2022. All SUMs had distal joint or proximal amputations. Primary endpoints were overall survival (OS) and recurrence free survival (RFS). Kaplan-Meier estimates, and Cox univariate and multivariate analyses were performed. Tests were repeated on propensity score matched (PSM) populations in a 2:1 ratio. Results: 123 patients underwent resection with SLNB for SUM (n ​= ​27) and AM (n ​= ​96). Median follow-up was 9.2 years. Unadjusted median OS was 149.1 months for AM and 198.1 months for SUM. In the PSM comparison, median OS and RFS remained comparable between SUM and AM (149.5 months versus 198.1 months; p ​= ​0.612). Sentinel node positivity was associated with significantly worse overall survival outcome (Hazard Ratio 5.49; CI (1.59–18.97), p ​= ​0.007). In the PSM population, male sex was also associated with a significant hazard of death (HR 3.00, CI (1.03–8.71), p ​= ​0.043). Proximal amputations were associated with significantly worse OS (p ​< ​0.002) and RFS (p ​< ​0.01) compared to distal amputations in SUM. Conclusion: SUM was well-treated with distal amputations, and had better OS and RFS compared to SUM treated with proximal amputations. Sentinel lymph node status is an important prognostic factor for SUMs and AMs. SUMs can be treated similarly to AMs with comparably good long-term outcomes.