The retinoids are a class of compounds structurally related to Vitamin A. More than 2,500 retioids have been synthesized and biologically tested. The second generation included the aromatic retinoids etritinate and acitretin with an enhanced therapeutic ratio and the third generation the poly-aromatic retinoids with or without polar end groups. Nine retinoids were evaluated as chemopreventive agents in cancer by an international group of experts at a meeting scheduled for March 24-30, 1999. These include some in clinical use for psoriasis or severe acne, all-trans retinoic acid used in the treatment of acute promyelocytic leukemias and several in clinical trial for the prevention of second primary tumours in patients with head and neck tumours and breast cancer. The deliberations and conclusions from this meeting have been published as Volume 4 of the IARC Handbooks of Cancer Prevention.
Skin cancer is more common than any other type of cancer.
Three major types of skin cancer are the highly curable basal cell and squamous cell carcinomas and the more serious cutaneous melanoma. Sunlight is the major cause of skin cancer. Sunscreens were developed for prevention of sunburns and contain chemicals that reduce the amount of UVR reaching the skin. Since 1950, an increasing number of white people have used sunscreens to protect themselves either during intentional or unintentional sun exposure. There is evidence, however, that during intentional sun exposure many people use sunscreens to extend the time of exposure to the sun.