ESTRO 2024 - Abstract Book

S238

Brachytherapy - Gynaecology

ESTRO 2024

Diana Guevara Barrera 1,2 , Silvia Rodriguez Villalba 2 , Luis Suso-Martí 3 , Enrique Sanchis-Sánchez 3 , José Pérez Calatayud 4,5 , Francisco Blazquez Molina 4 , Maria J Pérez-Calatayud 6 , Manuel Santos Ortega 2 1 Universidad Católica de Valencia San Vicente Mártir, Escuela de Doctorado, Valencia, Spain. 2 Hospital Clínica Benidorm, Radiation Oncology, Benidorm, Spain. 3 Exercise Intervention for Health Research Group (EXINH-RG), University of Valencia, Department of Physiotherapy, Valencia, Spain. 4 Hospital Clínica Benidorm, Radiophysics, Benidorm, Spain. 5 Hospital Universitario y Politécnico La Fe, Radiophysics, Valencia, Spain. 6 Hospital Universitario y Politécnico La Fe, Radiation Oncology, Valencia, Spain

Purpose/Objective:

The use of Magnetic resonance imaging (MRI)-compatible brachytherapy (BT) applicators is standard for the treatment of locally advanced cervical cancer (LACC). MRI imaging provides a superior visibility of soft tissue compared to computed tomography (CT), allowing a better delineation of CTV, resulting in more accurate and generally smaller treatment volumes. There is a lack however, of commercially available MRI-compatible transperineal gynecologic interstitial brachytherapy (P-ISBT) applicators, to be used in the case of vaginal-involving tumours. These are treatments that require coverage of the entire vagina, vaginal vault, and/or surrounding tissues. Our institution designed in 2013 an MRI-compatible applicator combining an IC component (vaginal cylinder +/- intrauterine tandem), with a perineal template and Titanium needles (Lorca Marin S.A; Murcia, Spain). It is an attempt to combine the technical advantages of the MUPIT (Elekta AB, Stockholm, Sweden) and the imaging advantages of MRI-based planning, while preserving the stability, geometry, and robustness of the implant. The purpose of this work is the dosimetric and toxicity analysis of patients with recurrences of vaginal-involving tumours (gynecological tumors in vagina and primary vaginal tumours), treated with P-ISBT in our institution, being the main difference the possibility to incorporate MRI in volume definitions and dose-volume dosimetry. Forty-two women with vaginal-involving tumours have been treated with P-ISBT between 2005 and 2022 in our centre. Patients were treated with radical (primary vaginal or macroscopic relapse), or adjuvant intent. Most of them also received external beam radiotherapy (EBRT) with or without chemotherapy. P-ISBT was performed with either MUPIT (CT-based planning), or an institutional MRI-based applicator. Implants were performed by the same team of radiation oncologists, and following strictly the same treatment protocols, similarly to the dosimetric planning. Instead inverse planning or target point based, plan optimization was performed through the help of geometrical optimization, followed by a fine-tuning manual optimization, in order to avoid inner over-dose volumes. Volumetric and dosimetric parameters were compared in both types of applicators. Toxicity outcomes were also compared in both groups of patients, according to common terminology criteria for adverse events v5.0 (CTCAE v5.0). Statistics Package for Social Science (SPSS 24.00, IBM Inc., EE.UU.) was used for analysis. Material/Methods:

Results:

Eighteen (42.9%) patients were treated with MUPIT applicator, compared to 24 (57.1%) patients treated with MRI based applicator. Seventeen (40.5%) patients had cervical cancer vaginal vault relapse, 15 (35.7%) had endometrial cancer vaginal vault relapse, 1 (2.4%) patient had a vaginal tumor relapse, and 9 (21.4%) patients were primary vaginal tumours. Median age was 59 (39-78). 22 (52.4%) patients received chemoradiotherapy (CRT), and 8 (19%)