Laetrile

Systematic reviews

Researchers conducting a Cochrane systematic review were unable to find any randomised clinical trials assessing the effectiveness of Laetrile5. They concluded that there was no evidence that Laetrile was effective as an anti-cancer agent.

An earlier review reported that although beneficial results had been reported from best case series and case studies, as these do not include a comparison group, they do not provide good quality evidence. It concluded that there is no sound evidence that Laetrile is effective as an anti-cancer agent6.

Uncontrolled clinical trials

Two clinical trials have been conducted with Laetrile. In the first study (a phase I study n=6)7, two of the six people studied developed cyanide poisoning symptoms whilst undergoing oral Laetrile treatment. The second (phase II) clinical trial (n=175)8 tested a metabolic therapy programme (which included the use of laetrile in addition to a healthy vegan diet). Only one person showed any benefit from taking Laetrile (tumour shrinking). During Laetrile therapy 7% reported an improvement in ability to perform normal activities and 20% showed symptomatic relief. However, these benefits did not continue after the therapy ended.

Results of trials in Benzaldehyde9,10 (one of Laetrile’s breakdown products) showed that in the first trial, out of 57 people, 19 showed a complete eradication of the cancer and ten showed a reduction in tumour size; in the second study the cancer was eradicated in seven of the 65 people and 29 had a partial removal or reduction in their tumour. No toxicity was reported in either study, furthermore, the positive benefits of the benzaldehyde only continued while it was being continuously taken.

Preclinical and animal studies

Two animal studies of laetrile in rodents found no statistically significant increase in survival time11,12.

However, four positive animal studies using laetrile have been found. In the first study positive effects of Laetrile were seen only when it was administered to mice alongside vitamin A and enzymes13. In the second study researchers using cell cultures found that Laetrile stimulated the immune system in terms of more white blood cells adhering to prostate cancer cells14. In the third, using tumour cells created in the laboratory, researchers found that Laetrile could indirectly sensitize the oxygen-starved cells at the centre of a tumour to the lethal effects of gamma irradiation15. In the fourth study researchers cultured human bladder cells and treated them with Laetrile alone and in conjunction with an antibody chemically related to beta-glucosidase. They found no benefit from administering Laetrile alone, however, when the antibody was also added cancer cells were killed16.