Learning curve of MRI-based planning for high-dose-rate brachytherapy for prostate cancer

PURPOSE: To evaluate introduction of MRI-based high-dose-rate brachytherapy (HDRBT), including procedure times, dose-volume parameters, and perioperative morbidity. METHODS AND MATERIALS: Study included 42 high-risk prostate cancer patients enrolled in a clinical protocol, offering external beam radiotherapy + two HDRBT 8.5 Gy boosts. Time was recorded for initiation of anesthesia (A), fixation of needle implant (B), end of MR imaging (C), plan approval (D), and end of HDRBT delivery (E). We defined time A E as total procedure time, A B as operating room time, B C as MRI procedure time, C D as treatment planning time, and D to E as treatment delivery time. Dose-volume parameters were retrieved from the dose planning system. Results from the first 21 patients were compared with the last 21 patients. RESULTS: Total procedure time, operating room time, MRI procedure time, and treatment planning time decreased significantly from average 7.6 to 5.3 hours (p < 0.01), 3.6 to 2.4 hours (p < 0.01), 1.6 to 0.8 hours (p < 0.01), and 2.0 to 1.3 hours (p < 0.01), respectively. HDRBT delivery time remained unchanged at 0.5 hours. Clinical target volume (prostate+3mm) Dgo fulfilled planning aim in 92% of procedures and increased significantly from average 8.3 to 9.0 Gy (p < 0.01). Urethral D-0.1 cm3 and rectal D-2 (cm3) fulfilled planning aim in 78% and 95% of procedures, respectively, and did not change significantly. Hematuria occurred in (95%), hematoma (80%), moderate to strong pain (35%), and urinary retention (5%) of procedures. CONCLUSIONS: After introduction of MRI-based HDRBT, procedure times were significantly reduced. D-90 Clinical target volume(prostate) (+3mm) fulfilled constraints in most patients and improved over time, but not at expense of an increased urethral or rectal dose. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.