Late Rectal Complication in Patients Treated with High Dose Rate Brachytherapy for Stage IIB Carcinoma of the Cervix

Kim, Gwi Eon; Kim, Woo Cheol; Keum, Ki Chang; Suh, Chang Ok; Chung, Eun Ji

Abstract

PURPOSE: This paper reports a dosimetric study of 88 patients treated with a combination of external radiotherapy and high dose rate ICR for FIGO stage IIB carcinoma of the cervix. The purpose is to investigate the correlation between the radiation doses to the rectum. external radiation dose to the whole pelvis. ICR reference volume. TDF, BED and the incidence of late rectal complications, retrospectively
METHODS
AND MATERIALS: From November 1989 through December 1992, 88 patients with stage IIB cervical carcinoma received radical radiotherapy at Department or Radiation Oncology in Yonsei University Hospital. Radiotherapy consisted of 44-54 Gy(median 49 Gy) external beam irradiation plus high dose rate intracavitary brachy therapy with 5 Gy per fraction twice a week to a total dose of 30 Gy on point A. The maximum dose to the rectum by contrast(r,R) and reference rectal dose by ICRU 38(dr, DR) were calculated. The ICR reference volume was calculated by Gamma Dot 3.11 HDR planning system, retrospectively. The time-dose factor(TDF) and the biologically effective dose (BED) were calculated.
RESULTS
Twenty seven(30.7%) of the 88 patients developed late rectal complications : 12 patients(13.6%) for grade 1, 12 patients(13.6%) for grade 2 and 3 patients(3.4%) for grade 3. We found a significant correlation between the external whole pelvis irradiation dose and grade 2, 3 rectal complicaition. The mean dose to the whole pelvis for the group of patients with grade 2, 3 complication was higher, 4093.3+/-453.1 cGy, than that for the patients without complication 3873.8+/-415.6 (0.05p<0.1). The gradual increase in the frequency of grade 2, 3 rectal compication increased as a function of the dose of external beam therapyto the whole pelvis(midline shielding start dose) and total rectal dose. The mean total rectal dose by rectal barium(R) for the group of patients with grade 2, 3 rectal complication was higher, 7163.0+/-838.5 cGy, than that for the patients without rectal complication, 6772.7+/-884.0(p<0.05). There was no correlation of the rate of grade 2, 3 rectal complication with the ICR rectal doses(r,dr), ICR reference volume, TDF and BED.
CONCLUSION
This investigation has revealed a significant correlation between the dose calculated at the rectal dose by ICRU 38(DR) or the most anterior rectal dose by contrast(R), dose to the whole pelvis and the incidence of grade 2,3 late rectal complications in patients with stage IIB cervical cancer undergoing external beam radiotherapy and HDR ICR. Thus there rectal reference points doses and whole pelvis dose appear to be useful prognostic indicators of late rectal complication in high dose rate ICR treatment in cervical carcinoma.