Primary and secondary prevention in the reduction of cancer morbidity and mortality.

Overall, cancer is a highly preventable disease. Indeed, modifiable external factors, discovered by epidemiological studies during the last 50 years, account for a majority of all cancer deaths. In this review, we discuss briefly these factors and their contribution to the current burden of cancer with an emphasis on the developed countries. Needless to say, tobacco smoking remains the largest contributor to the cancer landscape, whilst the contribution of poor diet and obesity may be equally important, but much more difficult to quantify. Our main goal was to assess what prevention of cancer has accomplished and might accomplish in the next two decades. Based on (necessarily crude) estimates, age-adjusted mortality rates from cancer in year 2000 had been reduced by approximately 13% due to primary prevention and an additional 6% due to the combined effect of early diagnosis and screening (secondary prevention). According to a realistic goal for the year 2020, a further 29% reduction might be achieved by primary, and 4% by secondary prevention. The main contribution to such accomplishments would be a reduction in tobacco smoking, improvements in diet--including reduced alcohol intake--and arrest of the obesity epidemic, in part through increased physical exercise. Rather than being granted, these goals require great effort and major commitment from all those who share responsibility for public health.