What is laetrile?
Although the names laetrile, Laetrile®, and amygdalin are often used interchangeably, they are not the same product. The chemical make-up of Laetrile® patented in the United States is different from the laetrile/amygdalin produced in Mexico. The patented Laetrile® is a semi-synthetic form of amygdalin, while the laetrile/amygdalin manufactured in Mexico is made from crushed apricot pits. The studies discussed in this fact sheet used either Mexican laetrile/amygdalin or Laetrile®. The generic term “laetrile” will be used throughout this fact sheet except in cases where the patented version of Laetrile® is known to have been used in a study.
What is the history of the discovery and use of laetrile as a complementary or alternative treatment for cancer?
How is laetrile administered?
Have any preclinical (laboratory and animal) studies been conducted using laetrile?
Have any studies of laetrile been conducted in people?
In a case series published in 1953, 44 cancer patients did not show any measurable response to treatment with laetrile. Most of the patients who showed some improvement also received radiation therapy or anticancer drugs, so it is impossible to determine which treatment produced the benefit.
In another series of case reports published in 1962, 10 patients with metastatic cancer (cancer that has spread from one part of the body to another) were treated with a wide range of doses of intravenous Laetrile®. Pain relief was the primary reported benefit. Reduced swelling of lymph nodes and decreased tumor size were also reported. However, long-term followup with these patients was not performed, so it is not known how long the benefits lasted after treatment.
Benzaldehyde, which is produced when laetrile is broken down by the body, has also been tested for anticancer activity in humans. In two clinical series (case reports of a number of patients who are treated consecutively in a clinic), patients with advanced cancer who had not responded to standard therapy were treated with benzaldehyde. Some patients experienced a complete response (the disappearance of all signs and symptoms of cancer), while some had a decrease in tumor size. The responses to benzaldehyde lasted as long as the treatment continued. Almost all of the patients had been treated previously with chemotherapy or radiation therapy, but it is not known how soon treatment with benzaldehyde began after the other treatment ended.
In 1978, the National Cancer Institute (NCI) requested case reports from practitioners who believed their patients had benefited from treatment with laetrile. Ninety-three cases were submitted; 67 of these were complete enough to be evaluated. An expert panel concluded that two of the 67 patients had complete responses and four experienced a reduction in tumor size. Based on these six cases, NCI sponsored clinical studies with laetrile.
What clinical trials (research studies in humans) been conducted with laetrile?
The first trial, a phase I study tested the doses, method of administration, and schedule of administration of amygdalin in six cancer patients. Researchers found that amygdalin caused minimal side effects. However, two patients who ate raw almonds while taking amygdalin developed symptoms of cyanide poisoning.
In 1982, a phase II study with 175 patients looked at which types of cancer might respond to treatment with amygdalin. Most of the patients in this study had breast, colon, or lung cancer. Amygdalin was administered by injection for 21 days, followed by oral maintenance therapy using doses and procedures similar to those evaluated 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 54 percent of the patients, there was a measurable progression (growth) of cancer at the end of the treatment. All of the patients showed cancer progression 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. However, these improvements did not last once treatment ended. On the basis of this study, NCI concluded that no further investigation of laetrile was necessary.
No controlled clinical trials (trials that include a comparison group of patients who receive no additional treatment, a placebo, or another treatment) of laetrile have been conducted.
Have any side effects or risks been reported from laetrile?
The side effects of laetrile appear to depend on the method of administration. More severe side effects are experienced when laetrile is given by mouth than when it is given by injection.
Is laetrile approved for use in the United States?
Variations in commercial preparations of laetrile have been documented in Mexico, which is the primary supplier of laetrile. Incorrect product labels have been found, and samples contaminated with bacteria and other substances have been identified.
When considering complementary and alternative therapies, what questions should patients ask their health care provider?
What benefits can be expected from this therapy?
How are complementary and alternative approaches evaluated?
More information about how CAM approaches are evaluated can be found in the National Cancer Institute (NCI) fact sheet Complementary and Alternative Medicine in Cancer Treatment: Questions and Answers. This fact sheet can be accessed at http://cis.nci.nih.gov/fact/9_14.htm on the Internet, or by calling the Cancer Information Service (CIS) at 1–800–422–6237.
How can patients and their health care providers learn more about complementary and alternative therapies?
The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.
NCCAM and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the Web sites of over 1,800 journals, allowing users to view articles in full-text. (A subscription or other fee may be required to access full-text articles.) CAM on PubMed is available through the NCCAM Web site at http://nccam.nih.gov. It can also be accessed at http://www.ncbi.nlm.nih.gov/PubMed by selecting "Limits" and choosing "Complementary Medicine" as a subset.
The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via its Web site http://www.cancer.gov/cam on the Internet.
The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.