Ionizing (and ultraviolet [UV]) radiation has been used in a variety of therapeutic procedures for skin conditions, including tinea capitis, acne, and psoriasis. Generally, the therapeutic effectiveness of radiation on skin is based on its ability to inactivate cell division. The comparative resistance of skin to cell killing by radiation means that effective therapies require comparatively high radiation doses. At therapeutically effective doses, there is a small but distinct probability of cells surviving, either in the irradiation field or nearby, with genetic alterations sufficient to predispose them to neoplastic progression. Both ionizing radiation and UV radiation (UVR) are capable of inducing cancer in human skin, although their mechanisms of action appear to differ substantially.
The action of ionizing radiation as a skin carcinogen has been studied extensively in rodent skin.1 After exposure of rat or mouse skin to single doses of ionizing radiation, the incidence of several types of