Isolated Limb Infusion or Perfusion as First-Line Versus Second-Line Therapy for In-Transit Metastatic Melanoma.

Background: In-transit metastases (ITM) develops in 10% of patients with high-risk melanoma. Isolated limb infusion and perfusion (ILI/ILP) are well-established therapies for ITM, but the ideal line of therapy has not been defined. This study compared ILI/ILP as first- versus second-line therapy.

Methods: An international multi-institution retrospective study reviewed patients with unresectable ITM who underwent ILI/ILP from 2006 to 2023.

Results: The study was comprised of 364 patients (55% female) with a median age of 71 years. Of the 364 patients, 329 (90%) were treated with ILI/ILP as first-line therapy, and 35 (10%) were treated with ILI/ILP as second-line therapy. The median follow-up period was 3 years. Lower-extremity disease was present in 85% (n = 310) of the patients. The best response for ILI/ILP as any line of therapy was 54% complete response (CR), 29 % partial response (PR), 8.2% stable disease (SD), and 9.1% progressive disease (PD). The CR/PR/SD/PD rates for first- versus second-line therapy were respectively 55%/ 29%/ 7.5%/ 8.2% versus 41%/ 26%/ 15%/ 18% (P = 0.09). As first-line therapy, ILI/ILP was associated with a significantly higher overall response rate (ORR) of 84% versus 68% (odds ratio [OR], 2.9; 95% confidence interval [CI], 1.2-6.9; P = 0.02). The comparison showed no statistical difference in median in-field progression-free survival (PFS) (10.8 vs. 8.1 months; P = 0.2), out-of-field PFS (13.5 vs. 15.3 months; P = 0.4), or overall survival (OS) (4.1 vs. 4.5 years; P = 0.7).

Conclusion: For patients with unresectable melanoma ITM, ILI/ILP either as first- or second-line therapy provides high overall response rates. Although first-line therapy had a higher ORR, this did not translate to a difference in in-field PFS, indicating that ILI/ILP is indeed an effective salvage therapy also as second-line therapy.