A Comparison of the Acute Toxicity Profile between Two-dimensional and Three-dimensional Image-guided Radiotherapy for Postoperative Prostate Cancer

Aims: To compare acute gastrointestinal and genitourinary toxicity for patients positioned with an electronic portal imaging device (EPID) and patients positioned with kilovoltage cone beam computed tomography (CBCT) during postoperative prostate radiotherapy. Materials and methods: Between 1999 and April 2010, 196 prostate cancer patients were referred for postoperative salvage radiotherapy. Patient position was corrected using EPID (1999 to December 2006, n = 116) or CBCT (January 2007 to present, n = 80). The treatment technique, number of beams, dose prescription, dose computation algorithm and planning target volume margins were not altered over time. Grade 1-3 acute gastrointestinal and genitourinary toxicity were compared between the EPID group and the CBCT group. Results: The incidence of grade 1 and 2 genitourinary toxicity was significantly reduced by 17 and 14%, respectively, in the CBCT group compared with the EPID group (P < 0.05). This was mainly attributed to a decrease in the following grade 1 symptoms: frequency (P < 0.05), nocturia (P = 0.06) and urgency (P = 0.07). Grade 2 incontinence (P = 0.06) and frequency (P = 0.06) were lower in the CBCT group. Grade 3 genitourinary toxicity was comparably low (EPID 3% versus CBCT 1%). There was no significant difference in gastrointestinal grade 1-2 toxicity between both groups. No grade 3 gastrointestinal toxicity was observed. Conclusions: Patient positioning with CBCT significantly reduces acute genitourinary toxicity compared with positioning with EPID. (C) 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.