[Field cancerization and field therapy - the therapy of actinic keratosis by imiquimod].

Field cancerization is a phenomenon in which multiple cancers easily occur on a specific area by carcinogens such as alcohol or ultraviolet rays. Deficiency of aldehyde dehydrogenase-2 increases the level of formaldehyde when drinking, and is considered an important factor for causing middle or lower pharyngeal cancer and esophageal cancer. Multiple actinic keratoses frequently occur both in synchronism or asynchronism on elderly people as a consequence of cumulative ultraviolet exposure. Field therapy, the regional overall treatment of actinic keratosis which takes place on the same field, is made possible by external use of imiquimod cream. Imiquimod is a topical immune response modifier which is effective through toll-like receptor 7, and it has fewer recurrences of actinic keratoses than the existing treatment.