1. What is laetrile?

   Laetrile is a compound that has been used as an anticancer treatment in humans worldwide. It is not approved by the US Food and Drug Administration (FDA) as a treatment for cancer or any other medical condition. The term “laetrile” comes from 2 words (laevorotatory and mandelonitrile) and is used to describe a purified form of the chemical amygdalin. Amygdalin is a plant compound that contains sugar and produces cyanide. Cyanide is believed to be the active cancer-killing ingredient in laetrile. Amygdalin is found in the pits of many fruits and in raw nuts. It is also found in other plants such as lima beans, clover, and sorghum.

   The names laetrile, Laetrile, and amygdalin are often used in place of one another, but 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 partly synthetic (man-made) form of amygdalin, while the laetrile/amygdalin made in Mexico comes 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 summary except in cases when the patented version of Laetrile is known to have been used in a study.

2. What is the history of the discovery and use of laetrile as a complementary or alternative treatment for cancer?

   Amygdalin was first isolated in 1830 and was used as an anticancer agent in Russia as early as 1845. Its first recorded use in the United States as a treatment for cancer was in the 1920s. The early pill form of amygdalin was found to be too toxic, and work with the compound was stopped. In the 1950s, a reportedly nontoxic, partly synthetic form of amygdalin was made and patented in the United States as Laetrile. Laetrile gained popularity in the 1970s as a single anticancer agent and as part of a metabolic therapy program that included a special diet, high- dose vitamin supplements, and pancreatic enzymes (a group of proteins that aid in the digestion of food). By 1978, more than 70,000 people in the United States had reportedly been treated with Laetrile.

3. What is the theory behind the claim that laetrile is useful in treating cancer?

   Cyanide is thought to be the main anticancer ingredient in laetrile. Two other breakdown products of amygdalin, prunasin (which is similar in structure to Laetrile) and benzaldehyde, may also be cancer cell blockers. See the PDQ health professional summary on Laetrile/Amygdalin ¹ for more information on theory.

4. How is laetrile administered?

   Laetrile is given by mouth (orally) as a pill. It can also be given by injection into a vein (intravenously) or muscle. Laetrile is commonly given intravenously over a period of time and then orally as maintenance therapy (treatment given to help extend the benefit of previous therapy).

5. Have any preclinical (laboratory or animal) studies been conducted using laetrile?

   Preclinical studies have been done with laetrile either alone or combined with other substances. These studies tested the benefits of laetrile against cancer, the side effects of laetrile treatment, where and how laetrile breaks down in the body, and how laetrile and its breakdown products leave the body. Laboratory and animal studies have shown little evidence that laetrile is effective against cancer.

6. Have any clinical trials (research studies with people) of laetrile been conducted?

   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.

   Although many anecdotal reports (incomplete descriptions of the medical/treatment history of one or more patients) and case reports (detailed reports of the diagnosis, treatment, and follow-up of individual patients) are available, they provide little evidence to support laetrile as a treatment for cancer.

   The following has been reported from case series about the use of laetrile in patients with cancer:

   • A case series (a group or series of case reports involving patients who were given similar treatment) of 44 patients treated with laetrile was published in 1953. Most of the patients who showed some improvement also received radiation therapy or anticancer drugs, so it is not known 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 main reported benefit. Reduced swelling of lymph nodes and decreased tumor size were also reported. Long-term follow-up with these patients was not done, however, so it is not known how long the benefits lasted after treatment.
   
   
   
   • Benzaldehyde, which is made 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 had 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 were helped by treatment with laetrile. Ninety-three cases were submitted; 67 of these were complete enough to be evaluated. An expert panel concluded that 2 of the 67 patients had complete responses and 4 others had a decrease in tumor size. Based on these 6 cases, NCI sponsored clinical studies with laetrile.
   
   
   

   Findings from only 2 clinical trials with laetrile have been published. These trials, sponsored by NCI, were done in the late 1970s and early 1980s, and did not include a control group for comparison.

   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.
   
   
   
7. Have any side effects or risks been reported from laetrile?

   The side effects of laetrile treatment are like the symptoms of cyanide poisoning. These symptoms include:

   • Nausea and vomiting.
   • Headache.
   • Dizziness.
   • Blue color of the skin due to a lack of oxygen in the blood.
   • Liver damage.
   • Abnormally low blood pressure.
   • Droopy upper eyelid.
   • Trouble walking due to damaged nerves.
   • Fever.
   • Mental confusion.
   • Coma.
   • Death.

   The side effects of laetrile appear to depend on the way it is given. More severe side effects develop when laetrile is given by mouth than when it is given by injection. These side effects may be increased by:

   • Eating raw almonds or crushed fruit pits.
   • Eating certain types of fruits and vegetables, including celery, peaches, bean sprouts, and carrots.
   • Taking high doses of vitamin C.
8. Is laetrile approved by the FDA for use as a cancer treatment in the United States?

   The US Food and Drug Administration (FDA) has not approved laetrile as a treatment for cancer in the United States. The drug is made and used as a cancer treatment in Mexico.

   Laetrile compounds from Mexico, which is the primary supplier of laetrile, may vary in purity and contents. Products containing bacteria and other substances and products labeled incorrectly have been found.

Glossary Terms

A substance found in the pits of many fruits such as apricots and papayas, and in other foods. It has been tried in some countries as a treatment for cancer, but it has not been shown to work in clinical studies. Amygdalin is not approved for use in the United States. Also called laetrile.

An incomplete description of the medical and treatment history of one or more patients. Anecdotal reports may be published in places other than peer-reviewed, scientific journals.

A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.

A colorless oily liquid used as a flavoring agent and to make dyes, perfumes, and pharmaceuticals. Benzaldehyde is chemically related to benzene.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

The force of circulating blood on the walls of the arteries. Blood pressure is taken using two measurements: systolic (measured when the heart beats, when blood pressure is at its highest) and diastolic (measured between heart beats, when blood pressure is at its lowest). Blood pressure is written with the systolic blood pressure first, followed by the diastolic blood pressure (for example 120/80).

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin).

A group or series of case reports involving patients who were given similar treatment. Reports of case series usually contain detailed information about the individual patients. This includes demographic information (for example, age, gender, ethnic origin) and information on diagnosis, treatment, response to treatment, and follow-up after treatment.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

Treatment with drugs that kill cancer cells.

A case series in which the patients receive treatment in a clinic or other medical facility.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.

Cancer that forms in the tissues of the colon (the longest part of the large intestine). Most colon cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

A condition in which a patient is in a state of deep sleep and cannot be awakened. A coma may be caused by many things, including trauma, drugs, toxins, or certain diseases.

The disappearance of all signs of cancer in response to treatment. This does not always mean the cancer has been cured. Also called complete remission.

In science, a substance that is made up of more than one ingredient.

A mental state in which one is not thinking clearly.

In a clinical trial, the group that does not receive the new treatment being studied. This group is compared to the group that receives the new treatment, to see if the new treatment works.

A clinical study that includes a comparison (control) group. The comparison group receives a placebo, another treatment, or no treatment at all.

The process of identifying a disease, such as cancer, from its signs and symptoms.

The things a person eats and drinks.

The process of breaking down food into substances the body can use for energy, tissue growth, and repair.

The amount of medicine taken, or radiation given, at one time.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

Use of a syringe and needle to push fluids or drugs into the body; often called a "shot."

Into or within a vein. Intravenous usually refers to a way of giving a drug or other substance through a needle or tube inserted into a vein. Also called I.V..

A substance found in the pits of many fruits such as apricots and papayas, and in other foods. It has been tried in some countries as a treatment for cancer, but it has not been shown to work in clinical studies. Laetrile is not approved for use in the United States. Also called amygdalin.

A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.

Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.

A rounded mass of lymphatic tissue that is surrounded by a capsule of connective tissue. Lymph nodes filter lymph (lymphatic fluid), and they store lymphocytes (white blood cells). They are located along lymphatic vessels. Also called lymph gland.

Treatment that is given to help a primary (original) treatment keep working. Maintenance therapy is often given to help keep cancer in remission.

Treatment to correct changes in metabolism that can be caused by disease.

Cancer that has spread from the place in which it started to other parts of the body.

The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. The National Cancer Institute conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the National Cancer Institute Web site at http://www.cancer.gov. Also called NCI.

A feeling of sickness or discomfort in the stomach that may come with an urge to vomit. Nausea is a side effect of some types of cancer therapy.

A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.

Not harmful or destructive.

By or having to do with the mouth.

A protein secreted by the pancreas that aids in the digestion of food.

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

The first step in testing a new treatment in humans. These studies test the best way to give a new treatment (for example, by mouth, intravenous infusion, or injection) and the best dose. The dose is usually increased a little at a time in order to find the highest dose that does not cause harmful side effects. Because little is known about the possible risks and benefits of the treatments being tested, phase I trials usually include only a small number of patients who have not been helped by other treatments.

A study to test whether a new treatment has an anticancer effect (for example, whether it shrinks a tumor or improves blood test results) and whether it works against a certain type of cancer.

Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.

A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called irradiation and radiotherapy.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

In medicine, treatment that experts agree is appropriate, accepted, and widely used. Health care providers are obligated to provide patients with standard therapy. Also called best practice and standard of care.

Cancer that forms in tissues lining the stomach. Also called gastric cancer.

Adding nutrients to the diet.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

Having to do with substances that are man-made instead of taken from nature.

Treatment.

Having to do with poison or something harmful to the body. Toxic substances usually cause unwanted side effects.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancerous), or malignant (cancerous). Also called neoplasm.

A nutrient that the body needs in small amounts to function and stay healthy. Sources of vitamins are plant and animal food products and dietary supplements. Some vitamins are made in the human body from food products. Vitamins are either fat-soluble (can dissolve in fats and oils) or water-soluble (can dissolve in water). Excess fat-soluble vitamins are stored in the body’s fatty tissue, but excess water-soluble vitamins are removed in the urine. Examples are vitamin A, vitamin C, and vitamin E.

A nutrient that the body needs in small amounts to function and stay healthy. Vitamin C helps fight infections, heal wounds, and keep tissues healthy. It is an antioxidant that helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin C is found in all fruits and vegetables, especially citrus fruits, strawberries, cantaloupe, green peppers, tomatoes, broccoli, leafy greens, and potatoes. It is water-soluble (can dissolve in water) and must be taken in every day. Vitamin C is being studied in the prevention and treatment of some types of cancer. Also called ascorbic acid.

To eject some or all of the contents of the stomach through the mouth.