Geometrical sparing factors for the rectum and bladder in the prediction of grade 2 and higher complications after high-dose-rate brachytherapy for cervical cancer.
OBJECTIVE
This study aimed to assess the predictive values of geometrical sparing factors for the rectum and bladder in high-dose-rate intracavitary brachytherapy (HDRICB) for Grade 2 and higher late sequelae in patients with cervical cancer.


METHODS
A total of 392 patients were enrolled in this study. They were treated with external beam radiotherapy to the pelvis, after which HDRICB was performed using Ir-192 remote after-loading at 1-week intervals for three or four sessions. The geometrical sparing factor (GSF) was defined as the average of the ratios between the reference doses and the Point A dose.


RESULTS
A total of 46 patients (11.7%) had Grade 2 or higher late rectal complications (36 Grade 2, 9 Grade 3, and 1 Grade 4). In all, 32 patients (8.2%) had Grade 2 or higher late bladder complications (14 Grade 2, 16 Grade 3, and 2 Grade 4). Multivariate analysis demonstrated a high risk of rectal sequelae in patients who developed bladder complications (p = 0.0004, hazard ratio 3.54) and had a rectal GSF greater than 0.7 (p = 0.01, hazard ratio 1.99). The high risk factors for bladder complications were development of rectal complications (p = 0.0004, hazard ratio 3.74), concurrent chemotherapy (p = 0.0001, relative risk 3.94), and a bladder GSF greater than 0.9 (p = 0.01, hazard ratio, 2.53).


CONCLUSIONS
This study demonstrates the predictive value of GSFs in HDRICB for cervical cancer. Patients with rectal GSFs greater than 0.7 or bladder GSFs greater than 0.9 are at risk for Grade 2 and higher late sequelae.
Chen
Shang-Wen
SW
Department of Radiation Oncology, China Medical University Hospital, Taichung, Taiwan. vincent1680616@yahoo.com.tw
Liang
Ji-An
JA
Hung
Yao-Ching
YC
Yeh
Lian-Shung
LS
Chang
Wei-Chun
WC
Yang
Shih-Neng
SN
Lin
Fang-Jen
FJ
D000230:Adenocarcinoma / Q000532:radiotherapy; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects* / Q000379:methods; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D008875:Middle Aged; D011832:Radiation Injuries / Q000150:complications / Q000473:pathology / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects*; D012016:Reference Values; D012044:Regression Analysis; D012307:Risk Factors; D001743:Urinary Bladder / Q000528:radiation effects*; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D007496:Iridium Radioisotopes