Impact on rectal dose from the use of a prostate immobilization and rectal localization device for patients receiving dose escalated 3D conformal radiation therapy.
OBJECTIVE
When >25% of the rectum is irradiated to > or = 70 Gy, the risk of developing Grade 2 or higher rectal complications is significantly increased. This study evaluates the impact on dose to the rectum from the use of an intrarectal (IR) balloon device, previously shown to immobilize the prostate gland and localize the rectum, in patients receiving dose escalated 3-dimentional (3D) conformal radiation therapy.


METHODS
From July 2001 through February 2003, 28 consecutive patients with prostate cancer underwent computerized tomography-based simulation with and without the IR balloon in place. Treatment planning was performed for three clinical paradigms in which the IR balloon was not used at all (0 Gy), used during the cone-down for 15 treatments (28.35 Gy), or used for the entire course of 40 treatments (75.6 Gy). The three plans were compared for differences in the percent of rectum receiving >70 Gy.


RESULTS
Dose volume histogram (DVH) analysis revealed that the median(range) of percent rectal volume exceeding 70 Gy was 25% (12.7-41.5%), 7.5% (0.9-19.5%), and 3.6% (0-8.7%) for patients in whom the IR balloon was used for 0, 15, and 40 treatments, respectively. The percent of rectum exceeding 70 Gy was significantly different for all treatment plan comparisons (P < 0.0001).


CONCLUSIONS
Grade 2 or higher rectal toxicity may be minimized during dose escalated 3D conformal radiation therapy through the use of an IR balloon during the 3-week cone down portion of an 8-week treatment course.
Department of Radiation Oncology, The Brigham and Women's Hospital, Dana Farber Cancer Institute, Boston, MA, USA. adamico@lroc.harvard.edu
Mona V
MV
Sanghani
Jane
J
Ching
Delray
D
Schultz
Robert
R
Cormack
Marian
M
Loffredo
Elizabeth
E
McMahon
Clair
C
Beard
Anthony V
AV
D'Amico
D000368:Aged; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology* / Q000517:prevention & control*; D020266:Radiotherapy, Conformal / Q000379:methods*; D012007:Rectum / Q000473:pathology* / Q000528:radiation effects*; D012307:Risk Factors; D014057:Tomography, X-Ray Computed