Isolated Limb Infusion as First, Second, or Third or Later-Line Therapy for Metastatic In-Transit Melanoma.

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.