For years scientists have been trying to utilise liposomes ("tiny bubbles of fat which carry material round the body") in order to administer toxic drugs to the tumour. However a few questions arose; how would the liposomes know where the tumours are, and how would they release the drugs when they get there? Liposomes have the property of, when being above 42C , beings soluble allowing their material, which is held securely under 42C , to be released. The human body should never get above 42C so the altered liposomes are harmless until heat is applied. By putting a heat probe into tumour the toxins will be released and can target the tumour therefore stunting growth / killing the tumour.
http://www.bbc.com/news/health-34667804
http://www.bbc.com/news/health-34667804