Primary cancer prevention trials.

Great progress has been made in cancer chemoprevention during the past 2 decades. Nevertheless, the field could benefit from the experiences of investigators studying the prevention of cardiovascular disease. During the past 50 years, prevention of cardiovascular disease has gone from a dream to a reality, with major clinical impact. The trend during the last 30 years has been impressive and sustained. From 1987 to 1994, there was a sustained major decrease in age-adjusted mortality from coronary heart disease in both men (from 3.1 to 2.2 per thousand persons) and women (from 1.1 to 0.9 per thousand persons). This trend is believed to have resulted from improvements in the treatment of myocardial infarction and, more substantively, from improvements in secondary prevention. This explanation is consistent with earlier computer simulations of trends in cardiovascular mortality during the 1980s, which estimated that 25% of the declines were attributable to primary prevention and 70% were caused by reductions in risk factors or treatment. The greatest effect of primary prevention had previously been noted in the late 1960s and 1970s. Most of these important findings occurred before cholesterol-lowering drugs became widely available, so further improvements are expected. Researchers in cancer prevention should follow in the footsteps of their cardiovascular colleagues. The tools are now available to make prevention of cancer a clinical reality. As the science of prevention improves, it must be remembered that effective and efficient preventive services do not help if they are not used. It is difficult to motivate practitioners and patients to implement preventive services. Also, preventive services are often considered a luxury. Persons without health insurance and those covered by Medicaid are much more likely to be diagnosed with late-stage cancer; therefore, they are key cohorts to target for effective preventive approaches. Finally, the most effective cancer prevention program will probably use both rational drug therapy targeting specific risk factors and public health efforts to promote healthy lifestyle choices in the population at large.