Definitive radiotherapy based on HDR brachytherapy with iridium 192 in uterine cervix carcinoma: report on the Vienna University Hospital findings (1993–1997) compared to the preceding period in the context of ICRU 38 recommendations

Abstract

According to the reports described in the literature, fractionated HDR brachytherapy seems to represent one option for the primary treatment of cervical carcinoma. In order to render such treatment transparent and comparable for those interested in the field, we have attempted to report our recent experience obtained in Vienna from 1993-1997 using the terminology proposed by the ICRU report 38, focusing in particular on dose and volume reporting and a linear-quadratic model. Based on these parameters, a comparison with the preceding period in Vienna (LDR/HDR) has been made, with an attempt to correlate different methods and parameters with outcome. One hundred and eighty-nine patients (mean age 67 years) were treated with curative intent (stage Ia: 2, Ib: 11, IIa: 11, IIb: 79, IIIa: 19, IIIb: 59, IVa: 5, IVb: 3 patients) using a combination of intracervical high-dose rate (HDR) brachytherapy (ring-tandem applicator) and a box technique for external-beam therapy (EBT: 48.6-50 Gy, linac 25 MV). Small tumors were treated with 5-6 fractions of 7 Gy at point A and 50 Gy EBT (25 Gy in the brachytherapy reference volume) which is isoeffective to 76-86 Gy at point A. Large tumors received 3-4 fractions of 7 Gy after 50 Gy EBT with open fields, which is isoeffective to 82-92 Gy at point A. TRAK varied from mean 1.4 cGy (3 fractions) to 2.8 cGy (6 fractions) at one meter. 3-D treatment planning for brachytherapy was based on conventional X-rays and in 181/189 patients on computed tomography (CT) with the applicator in place. Computer-calculated volumes of the brachytherapy reference isodose (7 Gy/fraction) ranged from 46-155 ccm (mean 87 ccm); the respective mean hwt-volume (height x width x thickness) was 180 ccm. The 60 Gy HWT volumes (25 Gy from EBT) for the irradiation of small tumors ranged from 240 to 407 ccm (mean 337 ccm) and for larger tumors (50 Gy for EBT) from 452 to 785 ccm (mean 607 ccm). The mean dose for brachytherapy was 16.2 Gy (6.2-37.8 Gy) at the ICRU rectum reference point and 14.4 Gy (4.6-35.7 Gy) at the ICRU bladder point. Taking into account the dose for EBT, the mean isoeffective dose at the ICRU rectum reference point was 69.9 Gy (28.4-98.7 Gy). Overall treatment time was six weeks for small tumors and eight weeks for large tumors. After a mean follow-up of 34 months, actuarial pelvic control and disease-specific survival rates at three years were 77.6/68.6% for all patients, 100/77.1% for stage Ib, 100/100% stage IIa, 87.0/78.0% stage IIb, 52.7/52.1% stage IIIa, 69.1/58.6% stage IIIb and 60/53.3% stage IVa. According to the LENT/SOMA score which had been prospectively introduced, the actuarial late complication rate for grades 3 and 4 was 2.9% for the bladder, 4.0% for the bowel, 6.1% for the rectum and 30.6% for the vagina (shortening and obliteration); in total for all grades 23.6, 18.4, 24.2, and 67.6%, respectively. In our experience, HDR brachytherapy combined with EBT is an efficient method if sufficient radiation doses and volumes are applied, both with regard to tumor control and adverse side effects. In future, the therapeutic window will be increased by systematic integration of magnetic resonance imaging (MRI) into treatment planning, thus allowing for a highly individualized approach with further adaptation of radiation dose and volume both to the target and to the individual topography of organs at risk.