Isolated limb infusion and perfusion (ILI/ILP) has been a mainstay treatment for unresectable melanoma in-transit metastases (ITM), but increased use of immune checkpoint inhibitors (ICI) and intralesional therapy (talimogene laherparepvec [TVEC]) introduced several different management options. This study compares first-line ILI/ILP, ICI, and TVEC. Retrospective review from 12 international institutions included patients treated from 1990 to 2022 with first-line ILI/ILP, ICI, or TVEC for unresectable melanoma ITM. A total of 551 patients were treated, with ILI/ILP (n=356), ICI (n=125), and TVEC (n=70) with median follow-up of 5.5 years. Tumor burden was highest with ILI/ILP and lowest with TVEC (p =.002). Breslow thickness was lowest with TVEC (p =.007). TVEC was mostly used in stage IIIB disease versus IIIC for ILI/ILP and ICI (p =.01). Using ICI as the reference category, TVEC had the highest odds of a complete response (CR) (odds ratio, 1.96; p =.029) and a longer local progression-free survival (PFS) (hazard ratio [HR], 0.40; p =.003). ILI/ILP had shorter local PFS (HR, 1.72; p =.012), PFS (HR, 1.79; p <.001), distant metastasis-free survival (DMFS) (HR, 1.75; p =.014), overall survival (HR, 1.82; p =.009), and melanoma-specific survival (HR, 2.29; p =.004). Stage IIIB disease had longer DMFS (HR, 0.24; p <.001) compared to IIIC/D. TVEC as first-line therapy for unresectable melanoma ITM was associated with superior CR rates and local PFS. Notably, TVEC was used in patients with a lower Breslow thickness, disease stage, and tumor burden. Therefore, when compared to ILI/ILP and ICI, TVEC should be considered as first-line therapy for unresectable stage IIIB melanoma ITM with minimal tumor burden and lower Breslow thickness.
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