How well does it work?
"Powerful claims of dramatic anti-cancer effects have been made by distributors and hospitals in Mexico where Laetrile is used. However, none of these claims have been supported by research evidence.
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Powerful claims of dramatic anti-cancer effects have been made by distributors and hospitals in Mexico where Laetrile is used. However, none of these claims have been supported by research evidence.
Anthropological studies
Supporters of Laetrile often use anthropological evidence to back up their anti-cancer claims. Such evidence comes from studies of remote cultures who consume high levels of foods rich in nitrisolides (Amygdalin), for instance, the Hunza, aboriginal Eskimo, the Hopi and Navajo Indians (ref 10). However, it is important to remember that, even though studies of these populations have reported low incidences of cancer, this must be viewed in context. This is because other unmeasured variables may not have been accounted for (for instance, environmental factors, stressors, pollution levels, deaths due to other causes and genetic differences).
Preclinical and animal studies
Using rodent cancers transplanted into rats and mice, no beneficial effects of the administration of Laetrile were seen in terms of increase in survival time (ref 11). Similar results were obtained from another study where human breast and colon cancer cells were implanted into mice, here no anti-cancer effect of Laetrile was found (ref 12). A further seven studies using many different tumour models have also been conducted, all finding Laetrile has no beneficial anti-cancer effects. However, four studies have found positive results when Laetrile is used. In the first study positive effects of Laetrile were seen only when it was administered to mice alongside vitamin A and enzymes (ref 13).
"Animal studies have also shown that the toxicity of Laetrile seems to be dependent on the route of administration, since taking the product orally is associated with greater toxicity than intravenous administration
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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 cells (ref 14).
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 irradiation (ref 15).
In the fourth study researchers cultured human bladder cells in the laboratory 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 killed (ref 16). The results from this fourth study need to be replicated in animals before its use in humans can be considered.
Animal studies have also shown that the toxicity of Laetrile seems to be dependent on the route of administration, since taking the product orally is associated with greater toxicity than intravenous administration. This is because intestinal bacteria contain enzymes that promote the release of cyanide in the digestive system (ref 17).
Human clinical studies
In terms of the case studies, although a number of detailed reports exist (ref 18) they do not appear as published peer reviewed journal articles. Furthermore, the use of conventional/unconventional therapies in conjunction with Laetrile, and variations in dosage between patients and a lack of long-term follow-up complicates the evaluation of the data. This aside, reports of pain relief, reduction in swelling of lymph nodes and decreases in tumour size have been recorded (ref 19)
Benzaldehyde (one of Laetrile’s breakdown products) has also been tested for its anticancer properties in two clinical trials with people for whom conventional therapy had failed (refs 20, 21). Results 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. However, these two studies’ results have not since been replicated and neither study was a randomised controlled trial. Since no control condition was used in these studies it is impossible to say whether benzaldehyde had an anti-cancer effect.
Two clinical trials have been conducted with Laetrile. The first study (a phase I study) tested six people with various types of cancer who were given Laetrile (re 22). This study found that under controlled conditions of administering Laetrile, minimal toxicity was experienced. However, two of the six people studied developed cyanide poisoning symptoms after eating raw almonds whilst undergoing oral Laetrile treatment. The second (phase II) clinical trial (ref 23) tested 175 people with various types of cancer in otherwise general good condition and free of any other prior therapy for one month. These people were given Laetrile intravenously over 21 days, followed by oral doses to maintain levels of Laetrile in the body. Along side the patients in the Laetrile group were also given vitamins and pancreatic enzymes as part of a metabolic therapy programme (in addition to a healthy vegan diet). People were followed in this trial until there was evidence of cancer progression, clinical deterioration or elevated cyanide levels. Out of the 175 people studied only one person showed any benefit from taking Laetrile ( tumour shrinking). Fifty-four percent of people studied had disease progression at the end of the study and all had worsened seven months after Laetrile therapy was completed. 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. Blood cyanide levels were not elevated after intravenous therapy, but were higher after oral doses of Laetrile.
From this study it was concluded that no further investigation of Laetrile was warranted as this substance has no lasting positive benefits for various cancer types. However, concern has been raised over the methodology used in the study in that those patients studied were considered to be terminal, therefore a negative result was perhaps more likely to be found (ref 24). Since the last major study in 1982 and the decision to "close the books" on Laetrile, many conspiracy theories have surrounded the prohibition of Laetrile. Controversy surrounds Dr. Ralph Moss, a former employee of the Sloan-Kettering Institute in the US. In 1977, Moss exposed "hidden" results of a positive response to Laetrile in animals with induced cancer. This supposedly hidden study was conducted by a Dr. Sugiura, but was never published in a peer-reviewed journal.
Records also exist of a study with 257 patients conducted at the Oasis Hospital in Mexico (ref 25). This study shows positive results for treatment with people with various types of cancer (12% partial or complete recovery; 55% stabilizing for six months). However, this study has not been published in a peer reviewed journal, nor has it been replicated.
References
10. McCarrison, SR. “Nutrition and National Health.�? Journal of the Royal Society of Arts. 1936. lxxxiv, 1047, 1067, 1087.
11. Wodinsky, I, & Swiniarski, JK. Antitumour activity of amygdalin MF (NSC-15780) as a single agent and with beta-glucosidase (NSC-128056) on a spectrum of transplantable rodent tumours. Cancer Chemotherapy Reports. 1975; 59, (5): 939-50.
12. Overjera, AA., Houchens, DP., Barker, AD. et al. Inactivity of DL- amygdalin against human breast and colon tumor xenografts in athymic (nude mice). Cancer Treatment Reports. 1978; 62 (4): 576-78.
13. Manner HW, DiSanti SJ, Maggio MI, et al. Amygdalin, vitamin A and enzyme induced regression of murine mammary adenocarcinomas. Journal of Manipulative Physiolgical Therapy. 1978; 1 (4): 246-8.
14. Bhatti RA, Ablin RJ, & Guinan PD. Tumour-associated directed immunity in prostatic cancer: effect of amygdalin. IRCS Medical Science research Biochemistry. 1981; 9 (1): 19.
15. Biaglow JE, & Durand RE. The enhanced radiation response of an in vitro tumour model by cyanide released from hydrolysed amygdalin. International Journal of Radiation Biology. 1978; 33 (4): 397-401.
16. Syrigos KN, Rowlinson-Busza G, & Epenetos AA. In vitro cytotoxicity following specific activation of amygdalin by beta-glucosidase conjugated to a bladdercancer-associated monoclonal antibody. International Journal of Cancer. 1998; 78 (6): 712-9.
17. Newmark J, Brady, RO, Grimley, PM, Gal, AE, Waller, SG, & Thistlethwaite, JR. Amygdalin (Laetrile) and pruasin beta-glucosidases: Distribution in germ free rat and in human tumor tissue. Proceedings of the National Academy of Sciences of the United States of America. 1981; 78 (10): 6513-6.
18. Binzel, PE, Alive and Well, 1994. American Media Publishing, USA.
19. Navarro, MD. Five years experience with Laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum. 1959; 15 (suppl 1): 209-21.
20. Kochi, M, Takeuchi, S, Mizutani, T, et al. Antitumor activity of benzaldehyde. Cancer Treatment Reports. 1980; 64 (1): 21-3.
21. Kochi, M, Isono, N, Niwayama, M, et al. Antitumor activity of a benzaldehyde derivative. Cancer Treatment Reports. 1985; 69 (5): 533-7.
22. Moertel, CG, Ames, MM, Kovach, JS, et al. A pharmacologic and toxicological study of amygdalin. Journal of the American Medical Association. 1981. 245 (6): 591-4.
23. Moertel, CG, Fleming, TR, Rubin, J, et al. A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. New England Journal of Medicine. 1982; 306 (4): 201-6.
24. Moss, RW. The Cancer Industry: The Classic Expose on the Cancer Establishment. (1996). Brooklyn, NY: First Equinox Press.
25. Quackwatch topics [online]. 2004 [cited 2004 July 18]. Available from URL: http://www.quackwatch.org/01QuackeryRelatedTopics/Cancer/Laetrile.html
