Reduction of Irradiation Volume and Toxicities with 3-D Radiotherapy Planning over Conventional Radiotherapy for Prostate Cancer Treated with Long-term Hormonal Therapy

Background: As hormonal therapy has an influence not only on outcome but also on toxicities, we compare the efficacy of three-dimensional radiotherapy planning (3D-RTP) and of conventional radiotherapy (Conv-RT) in association with long-term hormonal therapy in reducing toxicity of treatment. Patients and Methods: A retrospective case-control study was performed comparing the frequency of radiation toxicity between 63 Conv-RT and 52 3D-RTP patients with locally advanced prostate cancer (intermediate to high risk) treated with combined hormonal therapy. The average duration of neoadjuvant treatment was 7 months (1-38 months) and that of adjuvant treatment was 38 months (4-94 months). Patients were treated with 70 Gy of box field radiotherapy for the same clinical target volume (60 Gy prostate + seminal vesicle and 10 Gy boost to prostate). Results: Treatment volumes (=X RL ×Y SI ×X AP , where X RL =right left length of anterior-posterior portals, X AP =anterior posterior length of lateral portals and Y SI =superior inferior length of anterior-posterior portals) were significantly smaller in the 3D-RTP group (630±130 cm 3 ) than in the Conv-RT group (1036±223 cm 3 ) (p