Experience from clinical trials in cancer prevention.

Abstract

Conduct of randomized, controlled, large-scale prevention trials is fundamental to the full assessment of the efficacy of interventions to prevent cancer. Clinical trials in cancer prevention, which include dietary modification and chemoprevention, are based on leads from epidemiological and laboratory studies. Dietary intervention trials involve the modification of overall eating patterns, whereas chemoprevention trials involve the administration of natural or synthetic substances reported to have anticarcinogenic properties, e.g. vitamins, minerals, and pharmaceuticals. Clinical/metabolic studies can help advance knowledge of the role of diet in the etiology and prevention of cancer by investigating the metabolism of factors thought to influence cancer risk; thus, these studies have the potential to provide a stronger scientific base for progression to randomized, controlled clinical trials. Cancer prevention trials supported by the National Cancer Institute include the Polyp Prevention Trial, which is testing a low-fat, high-fibre, and vegetable- and fruit-enriched eating pattern on the prevention of polyp recurrence, and the Nutrition Intervention Trials of Oesophageal Cancer in Linxian, China, which are testing the efficacy of vitamin-mineral supplements in the prevention of oesophageal cancer in high-risk populations. Results from clinical cancer prevention trials will enable investigators to establish more firmly the relationships between diet and cancer and to translate the information effectively into significant reductions in cancer incidence and mortality.