ESTRO 2025 - Abstract Book

S1523

Clinical – Mixed sites & palliation

ESTRO 2025

Purpose/Objective: Local treatment options for inoperable cardiac metastases or primary tumors are limited. Data on the efficacy and toxicity of cardiac radiotherapy are scarce, primarily limited to case reports. To address this, the multicenter prospective SHARP study was initiated to evaluate the safety and feasibility of stereotactic MRI-guided radiotherapy for inoperable cardiac or peri-/paracardial metastases. Material/Methods: Patients have been enrolled at 4 study centers (Heidelberg, Rome, Zurich, Munich) since 09/2022. The treatment consists of stereotactic adaptive MRI-guided radiotherapy (MRIgRT) in 5 fractions with 6 - 8 Gy to the PTV (80% isodose). The primary objective is to determine acute toxicity and feasibility of radiotherapy. In addition, local control and toxicity over 1 year as well as quality of life will be assessed (follow-up every 3 months, if possible, with imaging). Results: A total of 39 patients (23 men and 16 women) were included in the study (median age 60 years, range 26-90 years). The most common histology was sarcoma, followed by mesothelioma and malignant melanoma. The median PTV dose per fraction was 7 Gy (range 6 - 8 Gy to the 80% isodose). So far, 5 patients have completed 1-year follow-up and 12 patients have completed 9 months follow-up. One patient has discontinued radiotherapy due to poor general condition (transfer to palliative care, not related to radiotherapy), one patient was a screening failure. Acute toxicity at 3 months included only mild side effects CTC°1-2 (most commonly dyspnea, fatigue, pain). One patient complained of treatment-related fatigue CTC°3 at 6 months and one patient had a pericardial effusion CTC°3 at 6 months. 30 patients have reached the 3-month follow-up so far: 13 lesions showed a complete or partial response (43%), 14 were stable (47%), 3 (10%) were not evaluated (end of study, lack of imaging). In terms of SAEs, 2 patients developed pneumonitis following radiotherapy, while another patient experienced ventricular fibrillation 2 weeks after radiotherapy (though its association with RT is uncertain due to a pre-existing condition). Additionally, two patients suffered strokes that may possibly be related to radiotherapy. Conclusion: MRIgRT for cardiac malignancies offers a tolerable treatment option for inoperable cases, providing a promising approach for patients previously without treatment options. However, the poor prognosis of this patient cohort – frequently characterized by metastatic disease, limited systemic options and cardiac involvement - makes long-term follow-up challenging. Despite the challenges of long-term follow-up, this approach represents a significant advancement in care.

Keywords: MRIgRT, cardiac, SBRT

2590

Digital Poster Management of Diaphragm Motion with Non-Custom Abdominal Corset and Shallow Breathing in Stereotactic Body Radiotherapy: A Single-Center Study Meltem Kirli Bolukbas 1 , Melisa Bagcı Kilic 2 , Gulsen Pinar Soydemir 1 , Metin Figen 1 , Bilgehan Topalak 3 , Esengul Kocak Uzel 1 1 Radiation Oncology, Health Sciences University Bakirkoy Dr. Sadi Konuk Training and Research Hospital, Istanbul, Turkey. 2 Radiation Oncology, Marmara University School of Medicine, Istanbul, Turkey. 3 Medical Physics, Health Sciences University Bakirkoy Dr. Sadi Konuk Training and Research Hospital, Istanbul, Turkey

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