Can cyanide(of course in nanogram quantities) used for chemotherapy of cancer?

Years ago this was tried by some people who were taking laetrile treatments for cancer. Laetrile was a source of cyanide from bitter almonds or peach pits, which was supposed to help kill cancer cells but it pretty much kills cells all cells, (as does some chemo treatments) but there's a fine line between the lethal dose of cyanide and the dosage that could be used medicinally. Good though though and I'm sure medical science has considered it already and found it to be unfeasible.