The condition and the treatment
Melanoma is a type of skin cancer. Advanced melanoma is when the cancer can't be completely removed by surgery (unresectable) or has spread to other parts of the body (metastatic). One type of melanoma has a change in the cells called the 'BRAF V600 mutation'. This makes it produce too much BRAF protein, and this protein makes the cancer cells grow and divide.
Pembrolizumab (Keytruda) is a drug given by injection, which helps the body's immune system to recognise and destroy melanoma cells.
NHS Choices (www.nhs.uk) may be a good place to find out more.