THE ROLE OF CHEMOPREVENTION IN CANCER CONTROL

Chemoprevention can be defined as the use of chemical compounds or med icines to prevent the occurrence of precancerous lesions (markers) or to slow down or revert the progression of clinically established disea se. The use of randomized trial design is considered the gold standard for evaluating the preventive value of chemicals against cancer, sinc e they control for confounding and avoid information bias. The princip al school in relation to cancer control through chemoprevention is bas ed on studies of cancer and diet. Initially, ecological studies set th e cornerstone, but later case-control studies supported the hypothesis of an inverse association between foods and cancer risk (principally epithelial), suggesting that determined micronutrients participate as protection in this process. Other studies include specific chemical an alyses, which have potential problems that could lead to erroneous con clusions, such as sample and measurement errors. During this decade ra ndomized intervention trials have been carried out to test this hypoth esis, but conclusions have been so diverse and the designs used have b een so different in terms of levels of exposure, that consistent concl usions are not possible. We can conclude that using studies with rando mized, double-blind, controlled designs is interesting, but problems r emain to be solved, including: agent selection, the design to be chose n, and especially the balance between benefits sought and secondary ef fects, including cost-effectiveness, since some chemicals cannot compe te with other preventive or therapeutic measures.