Treatment planning aids in prostate cancer: friend or foe?
BACKGROUND
Rectal barium is commonly used as a treatment planning aid for prostate cancer to delineate the anterior rectal wall. Previous research at the Ottawa Regional Cancer Centre demonstrated that retrograde urethrography results in a systematic shift of the prostate. We postulated that rectal barium could also cause prostate motion.


OBJECTIVE
The study was designed to evaluate the effects of rectal barium on prostate position.


METHODS
Thirty patients with cT1-T3 prostate cancer were evaluated. Three fiducial markers were placed in the prostate. During simulation, baseline posterior-anterior and lateral films were taken. Repeat films were taken after rectal barium opacification. The prostate position (identified by the fiducials) relative to bony landmarks was compared before and after rectal barium. Films were analyzed using PIPsPro software.


RESULTS
The rectal barium procedure resulted in a significant displacement of the prostate in the anterior and superior direction. The mean displacement of the prostate measured on the lateral films was 3.8 mm (SD: 4.4 mm) in the superior direction and 3.0 mm (SD: 3.1) in the anterior direction.


CONCLUSIONS
Rectal barium opacification results in a systematic shift of the prostate. This error could result in a geographic miss of the target; therefore, alternate methods of normal tissue definition should be used.
Malone
S
S
Department of Radiation Oncology, Ottawa Regional Cancer Centre, Ottawa, Ontario, Canada. shawn.malone@orcc.on.ca
Donker
R
R
Dahrouge
S
S
Eapen
L
L
Aref
I
I
Perry
G
G
Szanto
J
J
D000368:Aged; D000369:Aged, 80 and over; D001466:Barium Sulfate; D003287:Contrast Media; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum
D003287:Contrast Media; D001466:Barium Sulfate