COMBINED CASTRATION AND FRACTIONATED RADIOTHERAPY IN AN EXPERIMENTAL PROSTATIC ADENOCARCINOMA

Purpose: The present study using the Dunning R3327-PAP rat prostatic a denocarcinoma model was designed to study the effect on tumor growth o f castration prior to or after irradiation with 20-25 Gy as compared w ith either irradiation or castration alone, Methods and Materials: Rat s were bilaterally orchidectomized, During the irradiation procedure t he nonanesthetized animals were held in a metallic frame with a strong cotton net and they were observed by means of a video camera. The sub optimal irradiation dose was given once daily with a 4-MeV linear acce lerator, 4-5 Gy/fraction, during 5 consecutive days. Tumor volumes and rat weights were followed, At the end point of the study the animals were sacrificed and the tumors were morphometrically analyzed. Results : The combination of irradiation and castration delayed tumor regrowth better than irradiation alone with the same suboptimal dose, Castrati on before irradiation delayed tumor regrowth more efficiently than cas tration after irradiation, However, castration alone delayed tumor reg rowth even more effectively than suboptimal irradiation doses combined with castration, Conclusions: In combination with suboptimal irradiat ion neoadjuvant androgen deprivation was more inhibitory to rat prosta tic adenocarcinoma regrowth than adjuvant androgen deprivation, Irradi ation with suboptimal doses combined with castration may cause an earl ier relapse to androgen-independent tumor growth than castration alone . (C) 1997 Elsevier Science Inc.