MRI Based 3D Brachytherapy Planning of the Cervical Cancer – Our Experiences with the Use of the Uterovaginal Vienna Ring MR‑ CT Applicator

Abstract

Uterovaginal brachytherapy planning is conventionally based on the use of two orthogonal Xray projections. Currently, there is a large development of 3D brachytherapy planning based on the fusion of CT and MRI, which takes into account the extent of the tumor and the location of organs at risk. In this work, we evaluated the dosimetric data and first clinical results in patients with inoperable cervical cancer using MRI/ CT compatible applicator enabling 3D planning. Between June 2012 and March 2013, we performed 52 uterovaginal applications in 13 patients with inoperable cervical cancer using Vienna Ring MR CT applicator. Planning was carried out by the fusion of MRI and CT. Target volumes and organs at risk delineation were carried out on the basis of GEC ESTRO and ABS recommendations as well as doses report-ing. Overall radiotherapy duration was 37- 52 days with median of 45 days. The median total dose delivered to the HR CTV was 88 Gy (70.7- 97.9) EQD2. The median single dose in brachytherapeutic applications was D90 = 6.45 Gy (3.2- 9.82). The median total doses delivered to the rectum, sigmoid colon and bladder were D2ccrectum = 64.2 Gy (54.3- 74.1), D2ccsigmoid = 68.6 Gy (57- 74.7) a D2ccbladder = 73.9 Gy (58.3- 92.6). In 11 patients (84.6%), complete locoregional remission was achieved, in the remaining two patients (15.4%), partial locoregional remission was achieved. Twelve patients (92.3%) had complete regression of the tumor in the cervix, one patient (7.7%) developed metastatic spread to the liver. Yet we did not observe manifestations of a higher degree of toxicity than the first grade, both GI and GU. Late GI toxicity was manifested in two patients (15.4%) and late GU toxicity was manifested in five patients (38.5%). 3D brachytherapy planning of inoperable cervical cancer using the fusion of MRI and CT conclusively raises the possibility of the dose escalation to the tumor and significantly spares the surrounding organs at risk. Subsequently, this way of planning leads to better local control of the disease and to lower radiation morbidity.