Adaptive radiotherapy for prostate cancer using kilovoltage cone-beam computed tomography: first clinical results.
OBJECTIVE
To evaluate the first clinical results of an off-line adaptive radiotherapy (ART) protocol for prostate cancer using kilovoltage cone-beam computed tomography (CBCT) in combination with a diet and mild laxatives.


METHODS
Twenty-three patients began treatment with a planning target volume (PTV) margin of 10 mm. The CBCT scans acquired during the first six fractions were used to generate an average prostate clinical target volume (AV-CTV), and average rectum (AV-Rect). Using these structures, a new treatment plan was generated with a 7-mm PTV margin. Weekly CBCT scans were used to monitor the CTV coverage. A diet and mild laxatives were introduced to improve image quality and reduce prostate motion.


RESULTS
Twenty patients were treated with conform ART protocol. For these patients, 91% of the CBCT scans could be used to calculate the AV-CTV and AV-Rect. In 96% of the follow-up CBCT scans, the CTV was located within the average PTV. In the remaining 4%, the prostate extended the PTV by a maximum of 1 mm. Systematic and random errors for organ motion were reduced by a factor of two compared with historical data without diet and laxatives. An average PTV reduction of 29% was achieved. The volume of the AV-Rect that received >65 Gy was reduced by 19%. The mean dose to the anal wall was reduced on average by 4.8 Gy.


CONCLUSIONS
We safely reduced the high-dose region by 29%. The reduction in irradiated volume led to a significant reduction in the dose to the rectum. The diet and laxatives improved the image quality and tended to reduce prostate motion.
Nijkamp
Jasper
J
Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Pos
Floris J
FJ
Nuver
Tonnis T
TT
de Jong
Rianne
R
Remeijer
Peter
P
Sonke
Jan-Jakob
JJ
Lebesque
Joos V
JV
D000368:Aged; D001003:Anal Canal / Q000000981:diagnostic imaging; D054893:Cone-Beam Computed Tomography; D004032:Diet; D005740:Gases; D006801:Humans; D007422:Intestines; D054368:Laxatives / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated; D012007:Rectum / Q000000981:diagnostic imaging; D047368:Tumor Burden; D014546:Urinary Catheterization / Q000295:instrumentation
D005740:Gases; D054368:Laxatives