EXTERNAL-BEAM ABDOMINAL RADIOTHERAPY IN PATIENTS WITH SEMINOMA STAGE-I - FIELD TYPE, TESTICULAR DOSE, AND SPERMATOGENESIS

Purpose: To establish a predictive model for the estimation of the gon adal dose during adjuvant para-aortic (PA) or dog leg (DL: PA plus ips ilateral iliac) field radiotherapy in patients with testicular seminom a. Methods and Materials: The surface gonadal dose was measured in pat ients with seminoma Stage I receiving PA or DL radiotherapy. Sperm cel l analysis was performed before and 1 year after irradiation, PA and D L radiotherapy were simulated in the Alderson phantom while we measure d the dose to the surface and middle of an artificial testicle, varyin g its position within realistic anatomical constraints. The symphysis- to-testicle distance (STD), field length, and thickness of the patient were experimental variables, The developed mathematical model was val idated in subsequent patients. Results: The mean gonadal dose in patie nts was 0.09 and 0.32 Gy after PA and DL irradiation, respectively (p < 0.001), DL radiotherapy, but not PA irradiation led to significant r eduction of the sperm count I year after irradiation, The gonadal dose -reducing effect of PA irradiation was confirmed in the Alderson phant om, A significant correlation was found between the STD and the gonada l dose during DL irradiation, A mathematical model was established for calculation of the gonadal dose and confirmed by measurements in pati ents. Conclusions: During radiotherapy of seminoma, the gonadal dose d ecreases with increasing STD. It is possible to predict the individual gonadal dose based on delivered midplane dose and STD. (C) 1997 Elsev ier Science Inc.