Sequencing in management of in-transit melanoma metastasis: Diphencyprone versus isolate limb infusion.

BACKGROUND: In-transit metastases (ITMs) in melanoma are associated with poor prognosis, however a significant proportion of these patients survive for extended periods without further disease progression. We routinely use locoregional treatment e.g. Diphencyprone (DPCP) and/or isolated limb infusion (ILI) as long-term palliation. This study aimed to identify correct sequencing of these therapies based on disease burden and progression. METHOD: Retrospective evaluation of all melanoma patients with ITMs treated with DPCP/ILI/both from 2010 to 2017 at our Cancer Centre was performed. Patients were initially assessed in a multidisciplinary setting and empirically prescribed DPCP for low-disease burden, ILI for high-disease burden. Patient demographics, tumour characteristics, response to therapy, ITM progression and patient outcomes were analysed. RESULTS: 78 patients (M:F = 30:48), aged 47-95years (median 74years) treated with DPCP/ILI/both (n = 44/21/13) were identified. Progression-free survival (PFS) was significantly increased in patients responsive to DPCP or ILI as initial treatment. Patients who failed on DPCP and subsequently treated with ILI had a significantly increased PFS compared to DPCP alone (p = 0.026, HR = 0.048). This was not the case with patients who were treated with DPCP following failed ILI. All patients who failed to respond to the initial therapy progressed within 6 months. CONCLUSION: Our study shows that careful stratification ITM patients according to disease burden is fundamental to optimal outcomes. High-disease burden patients benefit from initial ILI; low-disease burden patients should commence on DPCP. ILI can be considered in DPCP patients who fail early. Systemic therapy should be considered when locoregional therapies fail after 12 months or after rapid relapse following ILI.