Chemoprevention of colorectal cancer

Epidemiological studies have emphasised the major role of diet in the aetiology of large bowel cancer. Attempts to identify causative or protective factors in epidemiological and experimental studies have led to some discrepancies. The time has come to test the most important hypotheses within the frame-work of intervention studies. Among studies specifically devoted to colorectal carcinogenesis, eight have been completed and five are ongoing. They evaluate the effect of the intervention on adenoma recurrence and, in three studies, on adenoma growth. Five intervention trials considering cardiovascular diseases and different cancer sites will provide data on the effect of the intervention on colorectal cancer incidence. Vitamins and antioxidants, fibre or calcium supplementation, aspirin therapy and dietary modifications are evaluated. Most of the available data do not support the idea of a protective effect of vitamins and antioxidants against colorectal carcinogenesis. It is too early to draw any conclusions on the effects of fibre, calcium supplementation, aspirin therapy and dietary intervention. The results of ongoing studies will be available within 2 years. If one of the evaluated interventions proves efficient, the benefits of a simple, safe and inexpensive prophylaxis for a very common cancer will be clear.