Prediction of Late Rectal Complication Following High-dose-rate Intracavitary Brachytherapy in Cancer of the Uterine Cervix / 대한방사선종양학회지

PURPOSE: Although high-dose-rate intracavitary radiotherapy (HDR ICR) has been used in the treatment of cervical cancer, the potential for increased risk of late complication, most commonly in the rectum, is a major concern. We have previously reported on 136 patients treated with HDR brachytherapy between 1995 and 1999. The purpose of this study is to upgrade the previous data and confirm the correlation between late rectal complication and rectal dose in cervix cancer patients treated with HDR ICR. MATERIALS AND METHODS: A retrospective analysis was performed for 222 patients with cervix cancer who were treated for curative intent with external beam radiotherapy (EBRT) and HDR ICR from July 1995 to December 2001. The median dose of EBRT was 50.4 (30.6~56.4) Gy with a daily fraction size 1.8 Gy. A total of six fractions of HDR ICR were given twice weekly with fraction size of 4 (3~5.5) Gy to A point by Iridium-192 source. The rectal dose was calculated at the rectal reference point using the barium contrast criteria. in vivo measurement of the rectal dose was performed with thermoluminescent dosimeter (TLD) during HDR ICR. The median follow-up period was 39 months, ranging from 6 to 90 months. RESULTS: Twenty-one patients (9.5%) experienced late rectal bleeding, from 3 to 44 months (median, 13 months) after the completion of RT. The calculated rectal doses were not different between the patients with rectal bleeding and those without, but the measured rectal doses were higher in the complicated patients. The differences of the measured ICR rectal fractional dose, ICR total rectal dose, and total rectal biologically equivalent dose (BED) were statistically significant. When the measured ICR total rectal dose was beyond 16 Gy, when the ratio of the measured rectal dose to A point dose was beyond 70%, or when the measured rectal BED was over 110 Gy3, a high possibility of late rectal complication was found. CONCLUSION: Late rectal complication was closely correlated with measured rectal dose by in vivo dosimetry using TLD during HDR ICR. If data from in vivo dosimetry shows any possibility of rectal bleeding, efforts should be made to reduce the rectal dose.

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

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.