Variation of small bowel sparing with small bowel displacement system according to the physiological status of the bladder during radiotherapy for cervical cancer.
OBJECTIVE
To evaluate the reproducibility of small bowel displacement system (SBDS) volumetrically using weekly CT throughout a regimen of radiotherapy for the treatment of cervical cancer.


METHODS
From October 2004 to January 2005, 10 consecutive patients who received pelvic radiation therapy for uterine cervical carcinoma with the SBDS were included in this study. With the patient laid prone on the conventional simulator table, the Styrofoam compression device is placed under the lower abdomen of the patient. Next, CT scan images, first two sets of without and with the SBDS, followed by with SBDS once a week for 3 weeks consecutively after the beginning of radiotherapy, were taken. Radiation planning was performed using standard pelvic box fields in 3-dimensional radiation treatment planning system. In each CT sets, we measured the identified organ volumes and the volume of small bowel irradiated in treatment portals. We used the regression analysis to know the correlation of the volume of small bowel irradiated according to the volume variation of bladder during radiotherapy.


RESULTS
The mean small bowel volume with SBDS of 10 patients during radiotherapy was reduced by 60.5% (from 32.5% to 78.2%), comparing to the small bowel volume without SBDS. The variation of small bowel volume reduction in each patient was ranged from 7.3% to 38.5% (mean: 20.5%). In spite of using the SBDS, the volume reduction of small bowel irradiated was affected significantly by the volume of bladder during radiotherapy. The variation of small bowel irradiated for five patients who had more than 10% small bowel volume variation was significantly correlated with the volume of bladder, but not for five patients less than 10% small bowel volume variation.


CONCLUSIONS
We confirm that in spite of the variation of bladder volume during radiotherapy, the SBDS is an effective method that can be used to displace the small bowel continuously away from the irradiated field for cervical cancer.
Park
Won
W
Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Ilwon-Dong 50, Kangnam-ku, Seoul, Korea.
Huh
Seung Jae
SJ
Lee
Jeung Eun
JE
Han
Youngyih
Y
Shin
Eunhyuk
E
Ahn
Yong Chan
YC
Lim
Do Hoon
DH
D000328:Adult; D000368:Aged; D003967:Diarrhea / Q000209:etiology / Q000517:prevention & control; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000033:anatomy & histology / Q000528:radiation effects*; D008875:Middle Aged; D011832:Radiation Injuries / Q000517:prevention & control; D011835:Radiation Protection / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000503:physiopathology*; D002583:Uterine Cervical Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*