A 3D conformal radiation therapy class solution for dose escalated prostate irradiation

Abstract

Prostate cancer is a dose responsive neoplasm i.e. the higher the dose of radiation administered, the more likely it is to attain local tumour control. However, high doses without careful conformal treatment planning leads to increased complication rates. This study aims to determine the ideal dosimetric and clinically relevant 3D conformal radiation therapy (3D-CRT) plan for 78 Gy dose escalated prostate treatment. A pilot study was performed on two patients using computed tomography (CT) images previously acquired to plan their treatment. The planning target volume in one patient encompasses the prostate only (PO) while the other had the prostate and seminal vesicles (PSV) contoured. Three senior radiation therapists and a radiation oncologist evaluated 10 optimised plans and recommended the top three techniques for further investigation. The top three techniques, 5-field (0, 90, 120, 240, 270 gantry angles), 6-field (30, 90, 120, 240, 270, 330 gantry angles) and 8-field (30, 60, 100, 135, 225, 260, 295, 330 gantry angles) were further applied to previously acquired CT images of another three patients, each contoured according to a standardised protocol. The median dose volume histograms (DVH) of the organs at risk (OAR) from five patients were compared to determine the best plan. The 6-field technique is the best option for dose escalated prostate irradiation. The 8-field technique produced the highest rectal dose while the 5 and 6-field techniques showed little variation (P = 0.239). The 6-field technique produced a plan with significantly less dose to the femoral head and neck compared to the 5-field technique (P = 0.001).