Human Chemoprevention Trials - Natural Agents in the Prevention of Cancer, part I

Alternative Medicine Review, Feb, 2001 by Davis W. Lamson, Matthew S. Brignall

Abstract

Data exist in the scientific literature showing reduction in the risk of tumor occurrence achieved by the use of nutritional and other natural materials. However, many trials that have attempted to prevent cancer occurrence with nutritional supplementation have found no effect or even increased tumor incidence. Several factors appear to be responsible for these disparate data, including the forms of nutrients used and the types of cancer being studied. In addition, combinations of nutrients have often been found to be more effective than single nutrient interventions. Appropriate use of supplemental nutrition, along with attention to pertinent dietary and lifestyle risk factors, comprise for the average person perhaps the best presently available strategy for prevention of the common types of malignancy.

(Altern Med Rev 2001;6(1): 7-19)

Introduction

The battle against cancer has been waged for several decades without resounding curative success from the use of chemotherapy or radiotherapy in most common solid tumors.[1] Much of the present day research directed against active malignancy has shifted toward identification of strategies affecting the growth rate or apoptosis of such cells so that life with cancer can be greatly extended without the deleterious effects of the more aggressive therapies.

The large majority of malignancies are attributable to dietary and lifestyle factors.[2] In addition there are many environmental chemical factors suspected of playing a sizable role in the occurrence of malignancies.[3] Given the poor success rate for treatment of most common tumors, it seems logical to focus attention on ways to prevent cancer occurrence.

Data exist in the scientific literature showing reduction in the risk of tumor occurrence achieved by the use of nutritional and other natural materials. Use of these materials along with attention to the dietary and lifestyle factors comprise for the average person perhaps the best presently available strategy for prevention of malignancy.

Background

It is now possible to perform genetic testing which can predict the likelihood of certain types of malignancies in an individual from a family appearing to have a predisposition toward a particular type of cancer. These individuals appear to be born with one mutated gene of the multiple significant mutations necessary to trigger most malignancies.[4] Being one step closer to developing a malignancy than the rest of the population does not predestine the person to the malignancy, but it does suggest that whatever means are available to retard subsequent gene mutations should be employed. Whether or not such a predisposed person is willing or able to obtain genetic testing, it is the recommendation of the authors that such person receive counseling as to preventive strategies to counteract their suspected predisposition.

The subject of cancer recurrence is more complex. Conventional oncology protocols call for use of procedures that are best indicated in a given situation (surgery, chemotherapy, radiotherapy, etc., or a combination), and if remission is achieved, treatment is followed by a period of sustained observation. Even during the period of remission, the presence of latent malignancy is considered possible.[5] In addition to the possibility of latent malignancy, a person who has undergone cancer treatment is at increased risk of developing a second primary malignancy.[6] These possibilities make long-term adjunctive therapy with natural supplements and dietary and lifestyle modifications after standard oncology therapies attractive and logical.

The occurrence of a malignant cell line suggests the presence of other cells -- with significant mutations but short of outright malignancy -- surrounding the tumor. Continuation of the same exogenous influences that created the first malignant cell could lead to additional significant mutations, such that these surrounding cells also progress to malignancy.

The question thus arises: can the next mutation(s) necessary to create malignancy be delayed or prevented? As an illustration, consider superficial bladder cancer. A standard therapy of surgery followed by intravesicular BCG application resulted in an 80-percent recurrence rate. Patients in this thai treated with high doses of four nutrients (vitamins A, B6 and C, and the mineral zinc) experienced a reduction in recurrence rate to 40 percent.[7]

The results from a number of studies concerning the limited cytotoxic effect of nutrients on malignant cells[8] argue against the possibility that supplementation with these four nutrients caused the regression of remaining malignant cells. The authors believe it is more likely the nutrients slowed additional mutation of non-malignant cells in the bladder that already had significant mutations.

The remainder of this article provides a summary of the human chemoprevention trials using natural agents. The second paper in this series will survey the animal and in vitro literature regarding the use of natural agents in chemoprevention. The concluding article will also contain nutritional recommendations for the primary and secondary prevention of colon, breast, and prostate cancers.