Thyroid Cancer, Papillary

This clinical trial is looking at a combination of drugs called vemurafenib and cobimetinib. Vemurafenib is approved as standard of care for adult patients with unresectable or metastatic melanoma. Cobimetinib is approved as standard of care in combination with vemurafenib for the treatment of adult patients with unresectable or metastatic melanoma. This means it has gone through clinical trials and been approved by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK. Cobimetinib and vemurafenib work in patients with these types of cancers which have certain changes in the cancer cells called BRAF V600 mutation-positive. Investigators now wish to find out if it will be useful in treating patients with other cancer types which are also BRAF V600 mutation-positive. If the results are positive, the study team will work with the NHS and the Cancer Drugs Fund to see if these drugs can be routinely accessed for patients in the future. This trial is part of a trial programme called DETERMINE. The programme will also look at other anti-cancer drugs in the same way, through matching the drug to rare cancer types or ones with specific mutations.