On the basis of standard laboratory tests and animal models used to screen anticancer drugs, there is little evidence to support a specific cancer -killing ability for laetrile. These investigations used numerous cultured cell lines and tumor models, and they explored the following issues: (1) whether laetrile, given alone or in combination with other substances, exhibits anticancer activity of any kind; (2) the toxic effects associated with laetrile treatment; (3) the location of laetrile breakdown in the body and how this breakdown occurs; and (4) the route(s) of excretion for laetrile and its breakdown products.
Animal studies of laetrile have used rodents,[1,2,3,4,5,6,7,8,9,10,11,12] dogs,[13,14] Reviewed in  rabbits, Reviewed in  and a cat. Early work led to the hypothesis that enzymes were necessary to release cyanide from amygdalin. When high levels of these enzymes were present, symptoms of cyanide poisoning were more pronounced. Reviewed in  In two studies sponsored by the National Cancer Institute and published in 1975, various rodent cancers (osteogenic sarcoma, melanoma, carcinosarcoma, lungcarcinoma, and leukemia) were transplanted into rats and mice.[2,3] In both studies, the animals were treated with intraperitoneal injections of amygdalin, with or without the enzyme beta-glucosidase. None of the solid tumors or leukemias investigated responded to amygdalin at any dose tested. No statistically significant increase in animal survival was observed in any of the treatment groups. Similar results were obtained in another study using human breast and colon cancer cells implanted into mice (xenograft models). Amygdalin at every dose level tested produced no response either as a single agent or in combination with beta-glucosidase. It was discovered that animals experienced more side effects when beta-glucosidase was given concurrently (at the same time) with amygdalin, compared with amygdalin alone.[2,3]
Caregiver burden is commonly used to describe multiple dimensions of distress that result from an imbalance between care demands and the availability of resources to meet those demands. Although quality of life is a multidimensional construct, the most studied aspect of quality of life in caregivers is psychological distress. Most family caregivers do not experience clinically significant levels of depression when providing care, but some studies report levels of depressive symptoms in caregivers...
Additional cell culture and animal studies involving more than a dozen other tumor models have been published.[1,4,5,7,8,10,11,16,17,18,19,20] In one study, preliminary findings by one of the principal investigators that amygdalin inhibited the growth of primary tumors and the incidence of lung metastases in mice bearing spontaneous (not treatment-induced) mammary adenocarcinomas could not be confirmed. However, positive results were obtained in four studies.[11,17,18,20]