Retinoids for the prevention of epithelial cancers: current status and future potential.

Prevention of epithelial cancers is needed, as the treatment of such cancers in the advanced state has failed. Vitamin A and its structural analogs called retinoids will prevent cancers of the lung, breast, bladder, stomach, and cervix in animals exposed to carcinogens. Synthetic retinoids, offer less toxicity than natural retinoids and may be acceptable to human trials. Identification of a suitable group at risk for an epithelial cancer which might be reasonably expected to benefit from retinoids should precede planning of a clinical trial.