There are anecdotal evidence that melanoma sufferers following the juicing diet by Dr Max Gerson responded well. Dr Gerson included a potassium Iodide solution in his diet.
Meanwhile, Dr Tullio Simoncini also uses topical Iodine to treat skin cancers. He seems to use a common Iodine tincture. In my experience alcohol containing Iodine tincture dries up quickly and "burn away" the skin under the area of application when enough is applied.