Prostate position variability and dose-volume histograms in radiotherapy for prostate cancer with full and empty bladder.
OBJECTIVE
To evaluate prostate position variability and dose-volume histograms in prostate radiotherapy with full bladder (FB) and empty bladder (EB).


METHODS
Thirty patients underwent planning computed tomography scans in a supine position with FB and EB before and after 4 and 8 weeks of radiation therapy. The scans were matched by alignment of pelvic bones. Displacements of the prostate/seminal vesicle organ borders and center of mass were determined. Treatment plans (FB vs. EB) were compared.


RESULTS
Compared with the primary scan, FB volume varied more than EB volume (standard deviation, 106 cm3 vs. 47 cm3), but the prostate/seminal vesicle center of mass position variability was the same (> 3 mm deviation in right-left, anterior-posterior, and superior-inferior directions in 0, 41%, and 33%, respectively, with FB vs. 0, 44%, and 33% with EB). The bladder volume treated with 90% of the prescription dose was significantly larger with EB (39% +/- 14% vs. 22% +/- 10%; p < 0.01). Bowel loops received > or = 90% of prescription dose in 37% (3% with FB; p < 0.01).


CONCLUSIONS
Despite the larger variability of bladder filling, prostate position stability was the same with FB compared with EB. An increased amount of bladder volume in the high-dose region and a higher dose to bowel loops result from treatment plans with EB.
Pinkawa
Michael
M
Department of Radiotherapy, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen, Germany. mpinkawa@ukaachen.de
Asadpour
Branka
B
Gagel
Bernd
B
Piroth
Marc D
MD
Holy
Richard
R
Eble
Michael J
MJ
D006801:Humans; D008297:Male; D009068:Movement; D010384:Pelvic Bones / Q000000981:diagnostic imaging; D011467:Prostate; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D012669:Seminal Vesicles / Q000000981:diagnostic imaging*; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014556:Urine