S49
Brachytherapy - Gynaecology
ESTRO 2026
and logistical constraints restrict its widespread implementation. This prospective study (CTRI/2024/12/077974) aimed to validate IBS-ABS-GEC ESTRO recommendations for CT-based contouring incorporating pre-brachytherapy MRI for target delineation and to assess the relationship between dosimetry, early clinical response and acute toxicity. Material/Methods: Fifty patients of locally advanced cervical cancer were prospectively enrolled. All received EBRT 45–46 Gy with weekly cisplatin, followed by image-guided brachytherapy (BT) using intracavitary (IC) or hybrid intracavitary–interstitial (IC+IS) techniques. Pre- brachytherapy MRI was performed 1–2 days prior to planned BT procedure. GTV/HRCTV volumes were estimated on pre-BT MRI. Subsequent CT-based planning involved HRCTV delineation on CT, closely referenced against pre-BT MRI volumes and OARs (bladder, rectum, sigmoid, bowel) were delineated. Planning aimed for HRCTV D90 ≥ 85 Gy EQD ₂ ( α / β = 10), with OAR constraints based on EQD ₂ ( α / β = 3). Dosimetric parameters (HRCTV D90, bladder, rectum, sigmoid, and bowel D2cc) were analyzed against clinical response at 3 months (RECIST v1.1) and acute toxicity (CTCAE v5.0). Results: The median age was 55 years (IQR 46–61). Majority had FIGO stage IIIC1 (44%) or IIB (34%) disease. Intracavitary application was performed in 62% and hybrid intracavitary–interstitial in 38%. The median HRCTV volume was 24.1 cc (IQR 16–32). Median HRCTV D90 EQD ₂ was 89.6 Gy (IQR 87.0–93.0). Complete response occurred in 92%, partial in 8%. HRCTV D90 did not differ statistically between complete and partial responders (p = 0.51) and showed no significant correlation with clinical response (r = –0.10, p = 0.49). Median D2cc EQD ₂ values were 81.3 Gy (IQR 73.5–86.6) for bladder, 59.8 Gy (IQR 56.4–67.4) for rectum, 68.3 Gy (IQR 62.1–74.6) for sigmoid, and 61.3 Gy (IQR 54.9–67.1) for bowel. Acute vaginal toxicity (grade 1–2) occurred in 14%, grade 3 in 4%, with no grade ≥ 4. Grade 1–2 GI toxicity occurred in 18%, with no acute bladder or rectal toxicity observed. OAR doses showed no significant organ-specific correlations (p > 0.05). Conclusion: CT-based contouring incorporating pre-brachytherapy MRI achieved adequate HRCTV coverage with OAR doses within tolerance. HRCTV dose showed no significant correlation with early response. This approach is a practical alternative to MRI-based IGABT and may support broader clinical implementation in limited-resource settings. Larger studies with extended follow-up are needed to confirm long-term outcomes and late toxicity. Keywords: CT-based contouring, Cervical cancer, Dosimetry
arm was within the predefined boundary and confirmed that short course was non-inferior to standard of care at one month (p = 0.40, mean difference=+4.2), 6 months (0.03, mean difference=+12.5) and 12 months (p = 0.35, mean difference=+6.2). Short course VCB was not found to be more cost effective than standard brachytherapy at one month (p.= 1.0) [LB2]Using EORTC EN24 for patient reported vaginal/sexual symptoms, there was no change in mean patient reported symptom score from baseline to 1 month, 6 months and 12 months. Using CTCAEv4, 3 patients experienced short-term AEs related to study treatment, 2 in the control arm and 1 in experimental arm. All study treatment-related AEs were grade 1. Sex was unenjoyable for the majority (81%) at baseline, 1 month, 6 months and 12 months.
Conclusion: Short-course VCB is non-inferior and demonstrates acceptable acute toxicity in patient-reported outcomes. By reducing treatment duration, it enhances patient convenience and has the potential to expand access to care in settings with constrained radiation resources Keywords: Endometrial, Brachytherapy, Quality of life. Prospective dosimetric–clinical correlation of CT- based contouring incorporating pre-brachytherapy MRI in cervical cancer brachytherapy Harismita Devi 1 , Srinivasa GY 1 , Swapnil Bisht 1 , Rimpi Singla 2 , Tulika Singh 3 , Arun Oinam 1 , Bhavana Rai 1 , Sushmita Ghoshal 1 1 Radiotherapy and Oncology, PGIMER, Chandigarh, India. 2 Obstetrics and Gynaecology, PGIMER, Chandigarh, India. 3 Radiodiagnosis, PGIMER, Chandigarh, India Purpose/Objective: MRI-based adaptive brachytherapy (IGABT) with applicator in-situ is the gold standard for locally advanced cervical cancer, but limited MRI availability Digital Poster 945
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