Power of Liquid Biopsy Tracking in Immunotherapy Treated Stage IV Melanoma

This prospective study will measure ctDNA in a simple plasma sample and using a dried blood spot assay, collected at the time of radiological disease progression. We will investigate the use of tumour informed and tumour naïve approaches, assessing targeted sequencing, copy number variations using whole genome low depth sequencing, fragmentomics and methylation as potential methods to improve molecular recurrence detection. We will also collect urine samples to investigate the use of cfDNA to detect relapse in the brain, which has been noted to be more challenging to detect using ctDNA in the blood than other sites of relapse. In addition, we will investigate the use of novel immunophenotyping technology through a collaboration with MelioHealth (IMU) in the same setting. The IMU platform combines high resolution cellular analysis and machine learning to enable high-content, high-throughput and real-time cellular immunophenotyping from less than 2ml of whole blood. We hypothesize that disease relapse following immunotherapy may detectably trigger a patient's immune system memory, which may be particularly important for those patients who do not shed ctDNA.