S465
Clinical - Gynaecological
ESTRO 2026
the univariate analysis, 2018 FIGO stage Ⅲ - Ⅳ A (65.3% vs 83.2%, P = 0.004) and HGB level less than 90 g/L (58.9% vs 76.8%, P = 0.024) were associated with worse PFS. Non- squamous cell carcinoma was associated with worse OS (48.6% vs 92.1%, P = 0.004). In the multivariate analysis, 2018 FIGO stage Ⅲ - Ⅳ A remained an independent predictor for worse PFS (P = 0.018), while underweight (P = 0.048) and non-squamous cell carcinoma (P = 0.005) were independent predictors for worse OS. Conclusion: A potential correlation exists between underweight and poor prognosis in cervical cancer patients, which will require confirmation through future prospective studies. Keywords: body mass index, underweight, cervical cancer Digital Poster Highlight 3275 Dosimetric Impact of Offline and Online Adaptive External Radiotherapy for Cervical Cancer: A Comprehensive Systematic Review Laura Siblini 1 , Inès Menoux 1 , Isabelle Chambrelant 1 , Florence Huguet 2 , Georges Noël 1,3 1 Department of Radiation Oncology, Institut de Cancérologie Strasbourg Europe (ICANS), Strasbourg, France. 2 Department of Radiation Oncology, Tenon Hospital, Sorbonne University, Paris, France. 3 Radiobiology Laboratory, Centre Paul Strauss, IIMIS – Imagerie Multimodale Integrative en Santé, ICube, Strasbourg University, Strasbourg, France Purpose/Objective: Adaptive radiotherapy (ART) aims to improve target coverage and reduce irradiation of organs at risk (OARs) by accounting for interfractional anatomical variations. In cervical cancer, tumor regression and organ motion can significantly affect dose delivery
despite image-guided intensity-modulated radiation therapy (IMRT). This systematic review evaluates the dosimetric performance of online and offline adaptive strategies compared with non-adaptive IMRT in cervical cancer. Material/Methods: This systematic review followed PRISMA guidelines. From 367 references, 17 studies
met the inclusion criteria, including prospective or retrospective analyses
comparing offline or online adaptive IMRT with standard non-adaptive IMRT in locally advanced cervical cancer ( ≥ FIGO IB2). Most were dosimetric simulations with cohort sizes ranging from 5 to 33 patients, exploring various adaptive strategies. Results: Seventeen studies were included, comprising seven assessing offline adaptation and fourteen assessing online approaches, with some studies evaluating both strategies.In non-adaptive IMRT, adequate target coverage was achieved only when using margins of ≥ 15 mm around the CTV, resulting in high doses to OARs. Offline adaptive radiotherapy, based on mid-treatment or weekly re-planning and using similar margins to non-adaptive treatments, provided limited or no improvement in target coverage, except for the ITV-based approach, which offered the best CTV coverage. OAR sparing with offline adaptation was inconsistent, showing only slight improvements, and in some ITV-based strategies even increased OAR dose. Offline ART therefore appears suitable mainly for slow or systematic anatomical changes.Conversely, online adaptive strategies demonstrated greater dosimetric benefits. Daily replanning guided by CT or MRI and plan-of-the-day (PoD) techniques provided optimal target coverage with significant dose reduction to OARs, even with reduced PTV margins of 3–5 mm. Reported reductions in V40Gy for key OARs were as follows: small bowel − 25% (PTV 3 mm) and − 18% (PTV 5 mm); bladder − 53% (PTV 3 mm) and − 44% (PTV 5 mm); rectum − 48% (PTV 3
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