Are you aware that you are acting very similarly to the individual caricatured in this steemit article?
Methadone does not help to destroy cancer in conjunction with standard therapy. Methadone might help to kill off glioma or glioblastoma cancer (brain tumor) cells in conjunction with standard therapy. And patients don't get exactly cured. They might live longer which is of course a very good argument for using this cheap drug and make the pharma companies cut their profits.
Saying Methadone is not the one-for-all cure of cancer ;-)