Comparative study of reference points by dosimetric analyses for late complications after uniform external radiotherapy and high-dose-rate brachytherapy for cervical cancer

Purpose: 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 and Materials: 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 Ir-192 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, 2.89-43.7) and total ICRU rectal dose greater than 16 Gy (p = 0.02;relative risk, 2.07;95% CI, 1.13-4.55). The high risk factors for bladder complications were seen in patients who developed rectal complications (p = 0.0001;relative risk, 15.2;95% CI, 2.81similar to44.9) and total ICRU bladder dose greater than 24 Gy (p = 0.02;relative risk, 8.93;95% CI, 1.79similar to33.1). Conclusion: 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. (C) 2004 Elsevier Inc.