ESTRO 2025 - Abstract Book

S877

Clinical - Gynaecology

ESTRO 2025

4227

Digital Poster External beam radiotherapy boost in gynecological tumours in which brachytherapy proves infeasible Diana Guevara Barrera 1 , Silvia Rodríguez Villalba 1 , Sabela Doval Raposo 1 , Judit Marin López 1 , José Pérez-Calatayud 1,2 , José D Lago Martín 1,3 , Manuel Santos Ortega 1 1 Radiation Oncology, Hospital Clínica Benidorm, Benidorm, Spain. 2 Radiation Oncology, Hospital Universitario y Politécnico La Fe, Valencia, Spain. 3 Radiation Oncology, Hospital Vithas Virgen del Consuelo, Valencia, Spain Purpose/Objective: Concurrent chemoradiotherapy (CRT) and subsequent brachytherapy boost is the standard-of-care for patients with locally advanced cervical cancer and a feasible treatment option in inoperable endometrial cancer. Brachytherapy is NOT optional and is crucial in the treatment of different gynecological tumors and usually employed alternatives offer poor rates of disease control, and higher morbidity/mortality 1,2,3,4 . However, in daily clinical practice, a certain proportion of patients are ineligible for BT. They pose a challenge when it comes to completing treatment programs, and there are currently no guidelines applicable to these scenarios. The purpose of our work is to describe the treatment approach employed in our institution, as well as clinical/toxicity outcomes. Material/Methods: Seven women received treatment with curable intent for histologically confirmed gynecological tumours in our centre between January/2022-July/2023. All patients had a diagnostic pelvic MRI. They received concurrent CRT 45-50.4Gy EBRT and, after re-evaluation MRI, were deemed ineligible for BT-boost. An EBRT boost was administered to these patients, with a previous planning CT scan with couch immobilization and rectal/bladder preparation. Three volumes were contoured with different prescription doses: 1) CTV: including the theoretical HR-CTV (cervix and tumor-involved areas), to receive 4Gy/fraction; 2) PTV: CTV+5mm geometrical margin, to receive 3Gy/fraction; 3) boost PTV: internal volume, CTV-5mm, adjusted manually, to receive 4.5Gy/fraction. Planning ensured compliance with GEC-ESTRO recommendations for OAR constraints 3,4 . Treatment was administered with VMAT, with daily cone-beam CT image guidance. Follow-up was performed at 1 month post treatment, and later every 3 months. Results: Median age was 69 years (46-90). Patient/treatment characteristics, motives for brachytherapy impossibility and treatment outcomes are detailed in Table 1. All patients had the same treatment prescription, except for Case 1, in which only 5 sessions of EBRT boost were administered since this patient was able to receive the first brachytherapy implant. Median D90-CTV (EQD2) was 82 Gy (75.1-96.7). No G>3 toxicities were reported. With a median follow-up of 19 months (12-32), 71.4% (5/7 patients) have no evidence of disease (NED). Two patients died from local disease progression. Both developed fistulae (one urinary, and the second one a vesico-recto-vaginal fistula) in relation to tumor infiltration. Conclusion: Brachytherapy is the gold-standard for tumour boost in gynecological treatments with curative intent. However, in patients in which brachytherapy is not an option, the present technique is a feasible alternative. The authors are fully aware that these treatments are not substitutes for brachytherapy and may only be considered in selected cases.