DO INFLAMMATORY PROCESSES CONTRIBUTE TO RADIATION-INDUCED ERYTHEMA OBSERVED IN THE SKIN OF HUMANS

Background: Two prospective trials were designed to determine whether there may be a role for inflammatory mediators in human skin erythema at both high and low doses per fraction and for 'out of field' effects . Methods: Trial 1. Effects of topical indomethacin (1%) and hydrocort isone (1%) applied before and during radiotherapy were compared for er ythema induced by 20 Gy in four fractions (n = 26, 6 MV). Trial 2. Eff ects of topical hydrocortisone (1%) applied before and during radiothe rapy and no medication were compared for erythema induced by 1, 3, 5 a nd 7 Gy in five fractions (n = 21, 120 kV). Erythema was measured usin g reflectance spectrophotometry (RFS) and laser Doppler (LD) on a week ly basis. Results: Trial I. A bi-phasic reaction time course was sugge sted in two-thirds of the cases. The first phase did not appear to be influenced by hydrocortisone cream but the second was significantly at tenuated. Indomethacin had no effect on either reaction phase. Erythem a measured several centimetres outside of the field was reduced by hyd rocortisone but not by indomethacin. Trial 2. Trial 2 confirmed the pr esence of measurable erythema, invisible to the eye, that coincided in its time course to the first phase of erythema noted in trial 1. This reaction was more intense than predicted by the LQ formula and was no n-significantly attenuated by topical hydrocortisone. RFS readings pro ved to be less subject to inter-and intra-patient variations than the LD unit used. Conclusion: Inflammatory responses may play a role in th e mediation of the erythematous response to radiation in human skin. F urther studies are warranted. (C) 1998 Elsevier Science Ireland Ltd.