ESTRO 2023 - Abstract Book

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Digital Posters

ESTRO 2023

Patients with bulky tumor ( ≥ 4cm), parametrial extension and lower vaginal involvement were selected to IC/IS brachytherapy. Target delineation defined by the GEC-ESTRO guideline with prescribed doses of 6 to 8 Gy in 4-6 fractions. Results The median follow-up time was 22 months (range 1 -85). Median clinical tumor at diagnosis was 5 cm. The FIGO stage IIB and IIIB were found 46.3% and 41.1%, respectively.Complete response rate was 66.3%. IC/IS brachytherapy and MRI before brachytherapy were used 44% and 50.7%, respectively. The Vienna ring applicator was used 47.2%. IC/IS was correlated with D90 HRCTV > 85 Gy in EQD2 (p=0.003). Median doses of D90 HR-CTV, D90 IR-CTV, D2cc bladder, D2cc rectum, D2cc sigmoid and D2cc bowel were 89, 65.1, 75.95, 67.5, 62.2 and 60.9 Gy in EQD2, respectively. Cervix and pelvic recurrent were 2.9% and 8.5%, respectively but distant metastasis was 23.5%. Late grade 3 proctitis and cystitis were 1.5% and 0.3%, respectively. Conclusion CT-based intracavitary and interstitial brachytherapy is feasible and achieved effective dose coverage which provides good local control with acceptable toxicity. However MRI-based brachytherapy is increasingly used, education and long term follow-up should be practice in the treatment of cervical cancer. 1 Homi Bhabha Cancer Hospital and Research Centre, Department of Radiation Oncology, Visakhapatnam, India; 2 Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria; 3 University Hospital Zürich, Department of Radiation Oncology, Zürich, Switzerland Purpose or Objective MRI based brachytherapy (BT) is considered standard for IGABT in cervical cancer, with excellent local control rates of over 90% at 5 years. However, access to MRI with brachytherapy applicator in-situ is limited in many high-volume centres across the globe. Recently, recommendations for target volume delineation in CT based IGABT have been published by IBS-ESTRO- ASTRO. A prospective international registration study is being planned to benchmark clinical outcomes of cervical cancer treated with CT based IGABT. To identify the need and interest in various CT based environments that can be potentially included in the protocol, a survey was conducted among selected centres with prior experience in IGABT. Materials and Methods The survey questionnaire was designed to estimate feasibility of implementing CT based IGABT with or without additional modalities like pre-BT MRI or Transrectal ultrasound (TRUS), in a multicentre setting. CT based planning for EBRT and BT, access to CT compatible hybrid IC+IS applicators, and prior experience with IGABT were considered pre-requisites for participation. Results Of the 28 centres that were approached, 20 centres from 7 countries (India, Egypt, Botswana, Brazil, Thailand, Singapore and Indonesia) responded and expressed interest to participate in a CT based IGABT registration study. Access to diagnostic MRI was reported by 80% of centres. IG-IMRT is routinely used for EBRT in 80% of centres. 85% reported feasibility of using pre-BT MRI in addition to CT based IGABT. While 60% centres have access to TRUS, only 20% have prior experience using TRUS for target definition and treatment planning. 70% centres reported use of IC+IS BT in >10% of cases. Confidence in target volume delineation on CT alone was reported to be high in 65% centres and moderate in 35% centres. Confidence in dose prescription to CT based target volumes was reported to be higher for IC alone (95% centres) compared to IC+IS (75% centres). Conclusion Results of our survey indicate that there is a significant interest among the centres in CT based IGABT registration study. It appears feasible to incorporate pre-BT MR and TRUS environments apart from CT alone environment in the registration study. There is a potential need for additional training in target delineation and treatment planning with CT based IGABT, especially with incorporation of TRUS. 1 Universidad Católica de Valencia San Vicente Mártir, Escuela de Doctorado, Valencia, Spain; 2 Hospital Clínica Benidorm, Radiation Oncology, Benidorm, Spain; 3 Hospital Clínica Benidorm, Radiophysics, Benidorm, Spain; 4 Hospital Universitario y Politécnico La Fe, Radiophysics, Valencia, Spain Purpose or Objective Magnetic resonance imaging (MRI)-compatible combined intracavitary/interstitial (IC/IS) applicators are commonly used in the image-guided adaptive brachytherapy (BT) treatment of locally advanced cervical cancer (LACC) and primary/recurrences vaginal tumours. But all the potential coverage allowed by IC/IS applicators is scarce if there is: medial or distal parametrial extension, unresponsive bulky disease, cervical tumors with vaginal extension of the middle or lower third, stage IV, unfavorable topography, very narrow vaginas or total/subtotal hysterectomy. In these cases, it is recommended to add a larger interstitial component using transperineal templates. Our institution designed in 2013 an MRI-compatible applicator combining an IC component (intrauterine tandem) with a perineal template and Titanium needles. It is an attempt to combine the technical advantages of the MUPIT (Elekta AB, PO-2145 Prelude to a registration study on CT based IGABT for cervical cancer: An international survey R. MIRIYALA 1 , M. Schmid 2 , C. Kirisits 2 , P. Petric 3 , U. Mahantshetty 1 PO-2146 Pre-plan Technique Benefice in Transperineal Brachytherapy D. Guevara Barrera 1,2 , S. Rodríguez Villalba 2 , J. Pérez-Calatayud 3,4 , F. Blazquez Molina 3 , M. Santos Ortega 2