10. The comparison between the three – field and four-field techniques of planning of radiotherapy in prostate cancer

Abstract

Purpose

evaluation 3-field(3F) and 4-field(4F) planning techiniques for patients with localized prostate cancer. Materials/methods: Five patients with prostate cancer (T3N0M0) were evaluated. CT images were obtained at 5 mm increments and were transferred to CadPlan_planning_workstation. The planning target volume (PTV) was defined as prostate and seminal vesicles with 15mm margins around clinical target volume (CTV) except prostate-rectum interface where 5 mm margin was applied. CTV was defined as prostate and seminal vesicles. Following organs at risk (OAR) were outlined: rectum, bladder, right femoral head. Following 3F and 4F plans were performed: 3F with angles (0deg-120deg-240deg; 0deg-90deg-270deg) and 4F (Odeg-90deg-180deg-270deg). We also created two versions of treatment plans including of energy; 6 MV and 20 MV for Clinac2300CD. Total dose was 74 Gy. Mean total doses of thirty plans in irradiated organs at risk (rectum, bladder and righ femoral head) were compared. For PTV mean and minimum dose were criteria for comparision of treatment plans. Results: There were no significant dose differenes between evaluated plans of treatment in PTV (0.05). Because mean dose in femoral head in each treatment plan was below tolerance dose, main dose-limiting organ was rectum and bladder. Lowest mean dose 42.7 Gy in rectum was achived by application of 3F technique of 20 MV(0deg-90deg-270deg). Bladder was also spared with the same 3F technique of 20 MV, where mean dose was 45.2 Gy. Conclusions: This study showed that the, T” three-field technique (an anterior and two opposing lateral fields) provided with 20 MV is optimal and assures the lowest rectal dose.