Comparative study of reference points by dosimetric analyses for late complications after uniform external radiotherapy and high-dose-rate brachytherapy for cervical cancer.
OBJECTIVE
This study aimed to correlate and compare the predictive values of rectal and bladder reference doses of uniform external beam radiotherapy without shielding and high-dose-rate intracavitary brachytherapy (HDRICB) with late sequelae in patients with uterine cervical cancer.


METHODS
Between September 1992 and December 1998, 154 patients who survived more than 12 months after treatment were studied. Initially, they were treated with 10-MV X-rays (44 to 45 Gy/22 to 25 fractions over 4 to 5 weeks) to the whole pelvis, after which HDRICB was performed using (192)Ir remote afterloading at 1-week intervals for 4 weeks. The standard prescribed dose for each HDRICB was 6.0 Gy to point A. Patient- and treatment-related-factors were evaluated for late rectal complications using logistic regression modeling.


RESULTS
The probability of rectal complications showed better correlation of dose-response with increasing total ICRU (International Committee on Radiotherapy Units and Measurements) rectal dose. Multivariate logistic regression demonstrated a high risk of late rectal sequelae in patients who developed rectal complications (p = 0.0001;relative risk, 15.06;95% CI, 2.89 approximately 43.7) and total ICRU rectal dose greater than 16 Gy (p = 0.02;relative risk, 2.07;95% CI, 1.13 approximately 4.55). The high risk factors for bladder complications were seen in patients who developed rectal complications (p = 0.0001;relative risk, 15.2;95% CI, 2.81 approximately 44.9) and total ICRU bladder dose greater than 24 Gy (p = 0.02;relative risk, 8.93;95% CI, 1.79 approximately 33.1).


CONCLUSIONS
This study demonstrated the predictive value of ICRU rectal and bladder reference dosing in HDRICB for patients receiving uniform external beam radiation therapy without central shielding. Patients who had a total ICRU rectal dose greater than 16 Gy, or a total ICRU bladder dose over 24 Gy, were at risk of late sequelae.
Chen
Shang-Wen
SW
Department of Radiation Therapy and Oncology, School of Medicine, China Medical University Taichung, Taiwan. vincent1680616@yahoo.com.tw
Liang
Ji-An
JA
Yeh
Lian-Shung
LS
Yang
Shih-Neng
SN
Shiau
An-Cheng
AC
Lin
Fang-Jen
FJ
D000230:Adenocarcinoma / Q000532:radiotherapy; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes; D016015:Logistic Models; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects*; D016019:Survival Analysis; D013997:Time Factors; D001743:Urinary Bladder / Q000528:radiation effects*; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D007496:Iridium Radioisotopes