The predictive value of skin XXXX for late radiation effects in different normal tissues.

@entity1 @entity8721
Alterations in the microcirculation and parenchymal cell loss are common phenomena after irradiation of different organs. Whether parenchymal cell loss is a process well dissociated from vasculoconnective damage, or a consequence of this, is much debated. However, comprehensive radiopathological studies have shown that vasculoconnective tissue is an important common target for late effects in various organs. Scoring of skin @entity8721 was used by us as a clinical assay of late tissue effects after different dose schedules. All studies were done prospectively with standardized skin area, field size and radiation quality. The @entity1 were scored regularly up to 10 years. The number of @entity1 at risk for a prescribed score versus time was calculated with the life-table method. The late effects after 5 X 2.0 Gy/wk, in the dose range 40 to 70 Gy and after 2 X 4.0 Gy/wk, in the dose range 40 to 56 Gy have been established. The skin dose is 90% of the referred dose. Dose-response curves, relating the proportion of @entity1 with a certain score at a fixed time and radiation dose and dose-latency curves, relating the latent period for a fixed proportion of @entity1 with a certain score and radiation dose, were constructed. The analysis shows that: ED10/5 yr and ED50/5 yr for 5 X 2.0 Gy/wk is 50 Gy and 65 Gy, respectively, for distinct @entity8721 ; The latent period, concerning both a certain frequency and degree of reaction, varies exponentially with dose level; The latent period for 50% of the @entity1 , to obtain a certain score, LP50, is correlated to that for 10%, LP10, with LP50/LP10 = 2.2 +/- 0.2 (S.D.). This correlation is independent of score, total dose, and fractionation; Isoeffective doses for 5 X 2.0 Gy/wk and 2 X 4.0 Gy/wk, determined from the dose-response curves, resulted in the repair exp N between 0.31 and 0.32 and alpha/beta ratio between 2.9 and 3.1 Gy and determined from the dose-latency curves in exp N between 0.30 and 0.32 and alpha/beta ratio between 3.4 and 2.9 Gy. In conclusion, frequent and careful follow-up with registration of normal tissue reactions, until at least 10% of the @entity1 have obtained the prescribed effect, is predictive for the further progression of the late effects. The fractionation characteristics for @entity8721 agree well with those for animal experimental morphological and functional endpoints for late effects in different organs and support the relevance of @entity8721 as a model for predicting late effects.
