REPORTS Induction of p53 Expression in Skin by Radiotherapy and UV Radiation: a Randomized Study

Background: p53 protein plays an im-portant role in the response to DNA damage, and radiotherapy can cause radiation dermatitis. p53 and p21 levels increase in vitro when DNA is damaged by UVA, UVB, or -radiation. To de-termine whether this response occurs in human skin and predicts the level of radiation dermatitis, we investigated levels of p53 and p21 in skin exposed to different types of radiation as part of a randomized study of women with breast cancer to evaluate topical ste-roid or emollient cream treatments for radiation dermatitis of their irradiated breast. Methods: After surgery but before receiving tangential 5-mV photo-beam radiotherapy (2 Gy and 54 Gy) to the affected breast paren-chyma, multiple areas on the backs of 50 women were irradiated with UVA and other areas were irradiated with UVB. Skin biopsy samples were taken from areas of normal unirradiated skin and all irradiated areas, and p53 and p21 were detected immunohistochemi-cally. All statistical tests are two-sided. Results: In skin irradiated with UVA or UVB, medians of 4.4 % (range