ESTRO 2025 - Abstract Book

S238

Brachytherapy - Gynaecology

ESTRO 2025

1 Radiation Oncology, Mahamana Pandit Madan Mohan Malaviya Cancer Centre & Homi Bhabha Cancer Hospital, (Units of Tata Memorial Centre), Varanasi, India. 2 Radiation Oncology, Homi Bhabha National Institute (HBNI), Mumbai, India. 3 Biostatistics, Mahamana Pandit Madan Mohan Malaviya Cancer Centre & Homi Bhabha Cancer Hospital, (Units of Tata Memorial Centre), Varanasi, India. 4 Biostatistics, Homi Bhabha National Institute (HBNI), Mumbai, India Purpose/Objective: Chemoradiation (CTRT) followed by brachytherapy is standard of care in locally advanced cancer cervix. With availability of CT/MR compatible tandem-ring and tandem-ovoid applicators, there has been a transition to 3D dosimetry and optimization in brachytherapy. Issues of coverage of lateral parametrial disease with the available applicators, while meeting OAR constraints, has resulted in an ascending interest in hybrid applicators. Geneva Applicator is a new generation of such applicator that enables Intracavitary(IC), Interstitial(IT) and Intracavitary with Interstitial(IC+IT) applications. Limited data is available on dosimetry analysis using the Geneva applicator. There is a need for validation of this user-friendly applicator in low medium income countries (LMIC), including India, where many patients with advanced disease would need needle placement for parametrial disease. Material/Methods: The present single arm prospective observational study involved 55 histo-pathologically proven FIGO stage IIB-IVA patients of cancer cervix. Patients underwent definitive CTRT (EBRT dose 45Gy in 25 fractions over 5 weeks) along with Cisplatin 40mg/m 2 followed by Brachytherapy that delivered 4 fractions of 7Gy each in 2 applications, using Geneva Applicator. Patients underwent planning MRI and CT scans with applicator in situ. Target and Organ-At-Risk (OAR) contouring was done on MRI. Dosimetry comparison was done using 3 treatment plans: (i) With Needle Optimized ( N_O ), (ii) Without Needle Optimized ( WN_O ), and (iii) Without Needle Non-Optimized ( Point A_WN_NO ). Doses to Gross Tumour Volume ( GTV ), High-risk Clinical Target Volume ( HRCTV ), Intermediate-risk Clinical Target volume ( IRCTV ), Bladder 2cc( B2cc ), Rectum 2cc( R2cc ), and Sigmoid 2cc( S2cc ) volumes were analyzed using these plans. Results: Three hundred and thirty plans were generated for analysis using 110 image sets (2 applications per patient) from 55 patients. The mean and median doses to target volumes and OAR are summarized in Table-1. The D90 HRCTV, D98 HRCTV, D98 IRCTV constraints were achieved in 94.5%, 92.7% and 98.2% N_O plans; in 63.6%, 72.7% and 92.7% WN_O plans, and in 98.2%, 90.9% and 100% Point A_WN_NO plans. Whereas, B2cc, R2cc, S2cc doses were achieved in 96.4%, 98.2%, and 96.4% N_O plans and in 96.4%, 98.2%, and 92.7% WN_O plans, they were achieved in only 29.1%, 89.1% and 29.1% Point A_WN_NO plans.