Rectal dose reduction using three-dimensional conformal radiotherapy for locally advanced prostate cancer: A combination of conformal dynamic-arc and five-static field technique

Background and purpose: The aims of this study are to compare our three-dimensional conformal radiotherapy (3D-CRT) plan using a combination of conformal dynamic-arc and five-static field (DASF) technique with other 3D-CRT plans for prostate cancer, and to estimate whether dose escalation is possible with DASF radiotherapy (DASF-RT). Methods and materials: Twenty patients with prostate cancer were included in this study. For each patient, five different treatment plans including DASF-RT were Created to entire prostate and seminal vesicles. Dose distribution and rectal dose-histogram (DVH) for each planning technique were compared. Results: In DASF-RT treatment plan, rectum V40, V50, V60, and V70 were 61.6%, 39.6%, 21.4%, and 0.6%, respectively. Compared with four 3D-CRT techniques, DASF-RT technique significantly reduce rectum V50 to V70 without increasing irradiated bladder and femoral head volumes. In addition, in the simulation of dose escalation to 76 Gy, the increase of each rectal dose-volume parameter (V40 to V75) was small enough. However, in dose escalation to 78 Gy, rectum V75 exceeded 5%. Conclusion: DASF-RT technique could significantly reduce rectal volumes receiving 50-70 Gy compared with other 3D-CRT techniques. DASF-RT was safe and feasible for dose escalation to 76 Gy in prostate radiotherapy. (C) 2008 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 90 (2009) 318-324