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).
Pembrolizumab (Keytruda) is a drug that helps the body's immune system to recognise and destroy melanoma cells. It is given by injection.
NHS Choices (www.nhs.uk) may be a good place to find out more.