Circulating tumour cell liquid biopsy in selecting therapy for recurrent cutaneous melanoma with locoregional pelvic metastases: A pilot study

Objectives: Circulating tumour cells (CTCs) from liquid biopsies provide an exceptional opportunity to obtain real-time tumour information and are under current investigation in several cancers, including cutaneous melanoma, but face significant drawbacks in terms of non-standardised methodology, low viable cell numbers and accuracy of CTC identification. In this pilot study, we report that chemosensitivity assays using liquid biopsy-derived metastatic melanoma (MM) CTCs, from 7 patients with stage IIIC, BRAF wild-type metastatic melanomas, localized exclusively to the pelvic region, un-eligible for immunotherapy and treated with melphalan hypoxic pelvic perfusion (HPP), is both feasible and useful in predicting response to therapy. Viable MM CTCs (> 5 cells/ml for all 7 blood samples), enriched by transient culture, were characterised in flow cytometry-based Annexin V-PE assays for chemosensitivity to several drugs. Results: Using melphalan as a standard, chemosensitivity cut-off values of > 60% cell death, were predictive of patient RECIST 1.1 response to melphalan HPP therapy, associated with calculated 100% sensitivity, 66.67% specificity, 33.33% positive predictive, 100% negative predictive, and 71.43% accuracy values. We propose that the methodology in this study is both feasible and has potential value in predicting response to therapy, setting the stage for a larger study. Trial registration Clinical Trials.gov Identifier NCT01920516; date of trial registration: August 6, 2013