S1105
Clinical – Upper GI
ESTRO 2026
Purpose/Objective: Neoadjuvant or definitive chemoradiotherapy (CRT) is a treatment option for esophageal cancer (EC). However, concerns persist regarding cardiopulmonary adverse effects and inconsistent target coverage due to anatomical changes between fractions. Promising results with increased target coverage, reduced organs-of-interest (OOI) doses and high complete response rates were observed in our previous analysis of CBCT-based online adaptive radiotherapy (oART) for EC, prompting the initiation of a prospective trial.1 This study presents preliminary results from the ongoing ARTEC trial, a prospective single-center study investigating oART for EC on the ETHOS platform. Material/Methods: This analysis included the first 14 of 30 planned EC patients enrolled in the ARTEC trial (Table 1). Prescribed oART dose was 50.4 Gy to the median PTV in 28 fractions with weekly carboplatin and paclitaxel. Treatment planning was based on a 4D-CT simulation. Contouring followed established guidelines2, however, CTVs were cropped from the heart and lungs, with a 5mm CTV-PTV margin applied. The primary endpoint was pulmonary adverse effects. Patients were assessed weekly during treatment and at 1, 3, 6, and 12 months post-oART to document adverse effects (CTCAE v5.0). CT scans at 3, 6, and 12 months assessed radiation-induced pulmonary changes. Prospectively collected dosimetric parameters for adapted and scheduled plans included CTV/PTV D1%, D95%, D99%; mean heart dose, heart V40Gy; lung V5Gy, V20Gy, mean lung dose; mean liver dose; and maximum spinal cord dose. Dose differences were compared using Wilcoxon signed-rank tests, with p-values <0.05 considered statistically significant.
Results: Adapted treatment plans achieved significant mean absolute improvements compared to scheduled treatment plans in CTVD99% (1.2%, p=0.006), PTVD99% (10.2%, p<0.001), CTVD95% (0.9%, p=0.011) and PTVD95% (3.5%, p=0.001). No significant differences were observed in heart, lung, liver, or spinal cord dose parameters (Table 2). Grade 3 acute adverse effects ( ≤ 3 months post-oART) occurred in 14.3%, with 2 cases of severe dysphagia—1 resolving spontaneously and 1 requiring balloon dilatation for radiation-induced esophageal stenosis. After a median follow-up of 8 months (range 1–18), only 1 (7.1%) grade 1 radiation-induced atelectasis was noted. Post- esophagectomy, 3 (21.4%) patients developed grade 3 aspiration pneumonia, and 1 (7.1%) had additional Grade 3 esophageal stenosis.
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