Relationship between early and late normal-tissue injury after postmastectomy radiotherapy.

Factors of importance in the development of telangiectasia were investigated in a series of 229 patients who, between 1978 and 1982, received postmastectomy radiotherapy with two different fractionation schedules. Patients who developed moist desquamation had a statistically significantly increased risk of developing telangiectasia after a specific course of radiotherapy. As an example the estimated incidence of severe telangiectasia after 44 Gy in 22 fractions increases from 27% to 49% in patients who developed grade greater than or equal to 2 moist desquamation as an early radiation reaction. A reanalysis of the Aarhus data with telangiectasia as the endpoint gave an alpha/beta ratio at 2.8 Gy (95% c.l. (-0.1, 8.1) Gy) and a relative biological effectiveness (RBE) of high energy electrons relative to 8 MV photons at 0.89 (95% c.l. (0.85, 0.93)). Patients age or the occurrence of severe erythema did not predispose to telangiectasia. A similar predisposition after moist desquamation was not seen for subcutaneous fibrosis. The RBE of high energy electrons relative to 8 MV photons for this endpoint was estimated at 0.88 (95% c.l. (0.86, 0.91].