S933
Clinical - Mixed sites & palliation
ESTRO 2026
WHO International Clinical Trials Registry Platform (ICTRP). Initial screening identified 1,249 registered studies. After excluding closed trials, verifying the adaptive component, and removing duplicates, 326 unique trials were retrieved; 127 met inclusion criteria (open clinical trial with ≥ 1 offline or online plan adaptation) and were analyzed. ART was defined as ≥ 1 offline or online plan adaptation performed after the initial treatment plan. For each eligible trial, we extracted standard descriptors (status, phase, design, sample size, site, endpoints) and ART-specific characteristics. ART goals were categorized as ARTex_aequo (no dose change to treatment site or OAR), escalation, de-escalation, or sparing organs-at- risk; adaptation approaches were classified as fixed- interval, triggered, serial, or cascade.1 Data were collected in a structured database for descriptive
appeared protective (OR = 0.65, 95 % CI 0.42–1.00, p ≈ 0.05). Conclusion: In this cohort of lung cancer patients treated with WBRT, PD-L1 expression did not significantly affect the predictive accuracy of the GPA, though a protective trend was observed. The strongest predictor of major prognostic deviation was the presence of active extracranial disease, highlighting its impact on survival estimation. These findings suggest that while PD-L1 alone may not alter GPA precision, integrating clinical and biological markers such as KPS and extracranial status could enhance prognostic calibration in the era of immunotherapy. References: 1. Sperduto PW et al. Initial Report of the Small Cell Lung Cancer GPA and Update of the Non-Small Cell Lung Cancer GPA (incl. PD-L1). IJROBP 2022.2. Oliver DE et al. The Lung Graded Prognostic Assessment: Continued Evolution of Brain Metastases Prognostication. IJROBP 2022; DOI: 10.1016/j.ijrobp.2022.05.045.3.Ribeiro LM et al. Development and adaptations of the Graded Prognostic Assessment (GPA) scale: a systematic review. Clin Exp Metastasis 2023; doi:10.1007/s10585- 023-10237-3. Keywords: GPA, WBRT Digital Poster Highlight 5030 Ongoing prospective studies on adaptive radiotherapy: A systematic review of clinical trials databases Maiwand Ahmadsei* 1 , Nicolas Bachmann* 2 , David Okle 1 , Konstantin Herfeld 2 , Hubert S. Gabry ś 1 , Sebastian M. Christ 1 , Nicolaus Andratschke 1 , Matthias Guckenberger 1 , Hossein Hemmatazad 2 , Michael C. Mayinger* 1 , Panagiotis Balermpas* 1 1 Department of Radition-Oncology, University Hospital Zurich, Zurich, Switzerland. 2 Department of Radition- Oncology, University Hospital Bern, Bern, Switzerland Purpose/Objective: Adaptive radiotherapy (ART) represents an innovation in precision and personalized cancer treatment through adaptation to anatomical and biological changes. Recently, a growing number of clinical trials have been initiated to evaluate clinical utility and implementation of ART. This study provides a comprehensive overview of ongoing ART trials registered on ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP). Material/Methods: We systematically searched ClinicalTrials.gov and the
analyses. Results:
Across 127 adaptive radiotherapy trials, the pelvis (52, 40.9%) and thorax (16, 12.6%) were the most common treatment site. Phase I/II compromised 39.4 % of the trials, 26 trials (20.5%) are randomized, and single- center designs dominate (96; 75.6%). The median patient number was 52 (mean 126; range 10–3000; IQR 30–129). Pelvic sites are most common (52; 40.9%), then thorax/mixed (16 each), head-and- neck/abdomen (15 each), CNS (8), and breast (5). The most commong primary tumors were prostate cancer (22, 17.3%) and lung cancer (16, 12.6%). Online adaptation predominates (105; 82.7%), with offline adaptation reported in 18 trials (14.2%). Serial ART predominates (97; 76.4%), followed by fixed-interval 29 (22.8%). ART goals emphasize ARTex_aequo maintenance (96; 75.6%), followed by escalation (18; 14.2%), OAR-sparing (11; 8.7%), and de-escalation (2; 1.6%). Primary endpoints focus on toxicity (49; 38.6%) and feasibility (20; 15.7%).
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