Risks and benefits of retinoids in the chemoprevention of cancer.

Chemoprevention of cancer is a new branch of clinical research; it may be defined as the reduction of cancer incidence by pharmacological means through the suppression of established malignant cell clones or through alteration in growth and progression of premalignant cell populations. In the last few years, this area of research has progressed dramatically from preclinical studies to phase I, II and III clinical trials. Among the various chemical or natural compounds used as chemopreventive agents, retinoids appear to be one of the most promising groups of agents. Analyses of preclinical and clinical studies have shown retinoids to be active in reversing skin and oral precancer, in preventing primary skin cancer, superficial bladder cancer, and second primary tumours associated with head and neck and lung cancers. Preclinical studies have shown evidence of the activity of fenretinide in breast cancer. Preliminary clinical data seem to show a protective effect of fenretinide against ovarian cancer. Current evidence therefore suggests that chemoprevention of cancer with retinoids is a promising path.