Experience from clinical trials in cancer prevention

Clinical trials in nutrition

Trials of nutritional intervention in a wide range of health and disease states, preventive and therapeutic, are required. Not only has the emergence of chronic non-communicable disease (CNCD) with acknowledged nutritional pathogenesis created this imperative need, but so also have other conditions which, previously, had not been regarded as nutritionally based. Among the latter are health problems associated with ageing: the menopause, a decline in immune function, and a decline in cognitive function. At the same time, there is a new set of materno-foetal and infant nutrition issues for investigation which relate to new food exposures and the long-term effects of nutritionally mediated gene expression. The emergence of the new food science of phytochemicals with human biological importance also sets the scene for their evaluation in traditional diets and novel foods. Such trials are more complex than comparable pharmacotherapeutic studies because of the complexity of food chemistry, as well as the food behavioural changes which may accompany a nutritional intervention, and the general problem of there not being a 'gold standard' for food intake methodology. Choice of study population is also a key issue in relation to the extrapolation of findings from a particular trial, with population representativeness being an advantage. In order to obtain useful information on manageable sample sizes, either intermediate end-points (short of morbidity and mortality) need to be studied or high-risk groups (such as the aged) need to be recruited. There are some unique ethical issues which must inform clinical nutrition trials. These include certain preventive imperatives like the right to be fed, the risks in disruption of food cultures and the need for food security and sustainability. Rapid changes in the food supply do, however, make such trials more important, while the value of food-health knowledge that cannot be obtained by trial must still be appreciated.

Traditional Chinese medicine in the treatment of breast cancer

The treatment of breast cancer involves multiple disciplines, and current recommendations are based on modern tenets of biology and pharmacology along with a growing body of evidence-based literature. Despite advances in screening, surgery, adjuvant radiation, and systemic therapy, as well as novel biologically targeted therapies, there are limitations to their benefits, especially in advanced disease. Complementary therapies including Oriental medicine have enjoyed a growing popularity as a less intensive and more "natural" approach to achieving health or improving quality of life. However, definitive literature in this area is scant and therefore has not been integrated into the mainstream medical community. Traditional Chinese medicine (TCM) may serve as a useful model for scientific inquiry since there is a standardized system of diagnostics and therapies, and this discipline is practiced worldwide. Still, the holistic and individualized nature of TCM presents challenges to rigorous clinical testing, and as a result, most published work in this field is in the form of anecdotal reports or uncontrolled series. Among the components of TCM, herbal or botanical agents possess complex biological activities that could affect many aspects of carcinogenesis such as cell growth and proliferation, apoptosis, host-tumor interactions, and immune function and differentiation. Despite a fairly extensive series of laboratory studies detailing many biological effects of botanical agents, few clinical trials have been completed to test specific hypotheses regarding the mode of action of TCM. Most TCM therapies have been empirically applied in a series of patients, with descriptive results provided. The summaries of a few studies highlighted in this review can provide some evidence of safety but generally do not possess the design and results to verify clinical effectiveness. Nevertheless, the theory of TCM coupled with laboratory studies and safety information can serve as a basis for the design of more definitive trials of TCM for specific indications in breast cancer. There are increasing interest and growing opportunities for investigative approaches that could ultimately verify or reject TCM and specific botanical agents. Some of these initiatives in the area of breast cancer prevention and treatment are outlined.

Dietary interventions of human carcinogenesis

The diet is a complex mixture that is associated with approximately 30% of human cancer in the U.S. Extensive laboratory studies indicate that the diet is composed of many mutagens/carcinogens as well as antimutagens/anticarcinogens. Overwhelming evidence from epidemiological studies indicates that a diverse diet that is high in fruits and vegetables and low in certain fats, along with moderate caloric intake and exercise, is most closely associated with reduced cancer risk. Dietary intervention studies using complex food items (fruits, vegetables, and fats) support these epidemiological observations; dietary interventions using single compounds (vitamins, antioxidants, etc.) have generally not. Estimates suggest that appropriate dietary changes could reduce the percentage of deaths due to prostate, colorectal, pancreatic, and breast cancer by >/=50%.

Antioxidants and carcinogenesis

It is established beyond doubt that free radicals in tissues and cells can damage DNA, proteins, carbohydrates and lipids. These potentially deleterious reactions are at least partly controlled by antioxidants capable of scavenging free radicals. It is widely believed that a proper balance between free radicals and antioxidants is essential for the health of an organism. A vast body of observational epidemiological studies has suggested that high intake of dietary or supplemental antioxidants protects against ischaemic heart disease, various types of cancer and several other diseases. Final proof for the beneficial effects of antioxidants can, however, be obtained from controlled studies. Conflicting results of the first three major clinical trials force us to postpone conclusions of the usefulness of antioxidant supplements in disease prevention until the other on-going trials have been published.