Laetrile is a substance with a long history in the United States. It can be obtained naturally as amygdalin from the pits of apricots and synthesized in the laboratory as laetrile. Many of my patients with cancer use laetrile and thousands of patients have used it in the past century. The most plausible biochemical pathway is that laetrile holds within it cyanide that can only be released enzymatically. Cancer cells hold greater amounts of the enzyme for this release reaction and cyanide is toxic to cells. Two products of laetrile, prunasin and benzaldehyde both seem to have tumor blocking properties as well. It is interesting that no controlled trials have been performed on this substance. There are case reports of benefits in cancer.

The following has been reported from these 2 clinical trials about the use of laetrile in patients with cancer:

• The first trial, a phase I study, tested doses, schedules, and ways to give amygdalin in 6 cancer patients. Researchers found that amygdalin caused very few side effects when given by mouth or intravenously. Two patients who ate raw almonds while taking amygdalin, however, developed symptoms of cyanide poisoning.
• In 1982, a phase II study with 175 patients looked at which types of cancer might benefit from treatment with amygdalin. Most of the patients in this study had breast, colon, or lung cancer. Amygdalin was given by injection for 21 days, followed by oral maintenance therapy using doses and procedures similar to those in the phase I study. Vitamins and pancreatic enzymes were also given as part of a metabolic therapy program that also included dietary changes. One stomach cancer patient showed a decrease in tumor size, which was maintained for 10 weeks while the patient was on amygdalin therapy. In about half of the patients, cancer had grown at the end of the treatment. Cancer had grown in all patients 7 months after completing treatment. Some patients reported an improvement in their ability to work or do other activities, and other patients said their symptoms improved. These improvements, however, did not last after treatment ended.

(quotation from the National Cancer Institute)

However, there are also case reports of cyanide toxicity in people who ingest laetrile so there is definite reason to be cautious.

A good patient of mine sent me this video of Dr. Ralph Moss giving his account of a cover-up of laetrile at Sloan Kettering. At this point I do not endorse laetrile nor do I discount it as a therapy. I maintain a goodwill and an open mind. If you do use it please avoid toxicity.

https://youtu.be/8A0TkWcHPAo

The National Cancer Institute notes:

No controlled clinical trials (trials that compare groups of patients who receive the new treatment to groups who do not) of laetrile have been reported.

and they summarize that:

Laetrile has shown little anticancer effect in laboratory studies, animal studies, or human studies (see Question 5 and Question 6).

The Cochrane review of laetrile concludes:

The claims that laetrile or amygdalin have beneficial effects for cancer patients are not currently supported by sound clinical data. There is a considerable risk of serious adverse effects from cyanide poisoning after laetrile or amygdalin, especially after oral ingestion. The risk-benefit balance of laetrile or amygdalin as a treatment for cancer is therefore unambiguously negative.

However, this seems more than a little unfair. There is a defined risk of cyanide toxicity and perhaps a lower risk of purchasing contaminated apricot seeds. These are likely avoidable if the therapy is used within certain guidelines. Cochrane places perhaps too much weight on randomized controlled trials (there are definite epistemological reasons one must be careful in equating “knowledge” with “statistical evidence from randomized controlled trials”). There is an “unknown” benefit in cancer mainly due to no funding for controlled trials but there is a trail of evidence pointing to benefit in case reports and non-randomized trials.

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