Despite recent advances in cancer treatment, little impact has been made on curing as opposed to controlling cancers over the last several decades. Part of the problem is that investigators have an incomplete understanding of how tumours behave as they evolve and in response to treatment. In this trial, the investigators hope to better understand the evolution of BRAF melanoma in response to drugs a patient may have received such as vemurafenib or dabrafenib. Importantly, the investigators want to understand how the tumours evolve resistance to these drugs and whether this can be predicted through blood tests, in particular of the circulating tumour DNA.