BACKGROUND: Ten percent of patients with melanoma develop in-transit metastases (ITM). Isolated limb infusion (ILI) is a well-established therapy for unresectable ITM on the extremities, but the ideal sequencing/line of therapy of ILI has not been defined. This study evaluates ILI as first-line, second-line, or third or later-line therapy.

METHODS: A retrospective review included all patients with unresectable ITM who underwent ILI from 2006-2023.

RESULTS: A total of 130 patients were identified, 61% female, median age of 71 (31-89) years. Median follow-up was 37.5 months. ILI was first-line therapy in 80% (n = 104), second-line in 15% (n = 19), and third or later-line in 5.4% (n = 7). Overall response rate (ORR) and complete response (CR) rates for ILI as any line of therapy were 74% and 41%, respectively. ORR for ILI as first, second, or third or later-line therapy were 78%, 63%, and 57%, respectively. CR rates for ILI as first, second, or third or later-line therapy were 42%, 37%, and 43%, respectively. There were no significant differences in ORR, progression-free survival (PFS), overall survival, or disease-free survival between therapy lines. Median PFS for ILI as first, second, or third or later-line therapy were 6.9, 5.4, and 18 months, respectively.

CONCLUSION: Patients responded well to ILI, whether or not they received previous therapies for unresectable ITM. First-line ILI appears to have a better ORR than later lines of ILI. Although sample size limited statistical significance, there was a 21% improvement in ORR when ILI was used as first-line vs third-line therapy, which is clinically meaningful. ILI is effective for unresectable melanoma ITM and can be used as salvage therapy.

Isolated limb infusion (ILI) is an excellent treatment option for patients with in-transit melanoma. In this study, patients responded notably well when ILI was used as first-line therapy, and also responded well when ILI was used as a salvage therapy.