Laetrile/apricot seeds/vitamin B17 for the treatment of cancer

Has anyone used apricot seeds/vitamin B17 seeds for the treatment of cancer (or probably oropharynx cancer)? Could you please tell me more about it? What would happen in case of a person having a stage IV cancer and had undergone 9 rounds of chemotherapy and 40 radiations of radiotherapy?? Where will I find those products??