ESTRO 2025 - Abstract Book

S1525

Clinical – Mixed sites & palliation

ESTRO 2025

recurrence-free survival at 6, 12, and 18 months. Initial results are based on 39 patients analyzed between September 2023 and November 2024, with a target enrollment of 60 patients.

Material/Methods: The study consists of two distinct phase II trials with both curative and palliative intent: one exploring superficial hyperthermia (CT1) for recurrent breast cancer and superficial tumors, and another investigating deep hyperthermia (CT2) for deep-seated tumors, pelvic relapses, and bone metastases. HT was delivered immediately after RT sessions using a capacitive radiofrequency device (Hy Deep 600), maintaining treatment for 60 minutes and achieving tissue temperatures of up to 41 – 42°C. Treatments were performed twice weekly on non-consecutive days. Data on toxicity, adherence, and oncologic outcomes were systematically collected using REDCap. Results: Among the 39 patients analyzed, more than 60% had breast cancer. Acute toxicity was evaluated, with 61.5% experiencing no adverse effects (Grade 0), 7.7% reporting Grade 1, and 15.4% experiencing Grade 2 toxicity. Grade 3 toxicity was observed in 15.4%, primarily as focal radiodermitis. Most Grade 3 events occurred in breast cancer patients, 40% of whom required bolus application. The overall toxicity profile was consistent with that observed for RT alone. Treatment adherence was high, with 89.75% of patients completing the protocol. Four patients discontinued early: one due to extensive radiodermitis and three due to pain or comorbidities. Among those completing HT, 88.7% tolerated treatment well, though power reductions were needed in 11.3% of cases to manage discomfort, such as pain or burning sensations. Preliminary oncologic outcomes were favorable. Patients with breast cancer relapse treated with curative intent achieved 100% local control at six months with no further relapses. Pain relief was achieved in 75% of metastatic cases. Early mortality was linked to progression of advanced pelvic disease.

Conclusion: Hyperthermia combined with RT is safe, well-tolerated, and achieves promising local control and palliative outcomes with manageable toxicity. Final results aim to provide stronger support for its integration into oncologic treatment protocols, with plans for multi-center phase III trials to confirm the long-term benefits of this approach.

Keywords: Hyperthermia, clinical trials

References: Oldenborg et al. (2019). Efficacy of palliative radiotherapy combined with hyperthermia. Cancers. Datta NR, et al. (2016). Hyperthermia and radiotherapy in breast cancer: A meta-analysis. Int J Hyperthermia. Kaidar-Person et al. (2017). Re-irradiation and hyperthermia in breast cancer. Clinical Oncology. Van der Zee J, et al. (2000). Radiotherapy alone vs. radiotherapy plus hyperthermia in advanced pelvic tumors: A randomized trial. Lancet. Mau-Shin Chi et al. (2018). Combined external beam radiation and hyperthermia vs. radiation alone for painful bone metastases: A phase 3 randomized trial. National Cancer Institute (NCI). Common Terminology Criteria for Adverse Events (CTCAE) v5.0, November 2017.

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Digital Poster Prospective clinical trial using gantry-less image-guided proton therapy for locally recurrent head and neck and brain malignancies Philip Blumenfeld 1 , Alexander Pryanichnikov 2,3 , Yair Hillman 1 , Ella Wajnryt 1 , Aviad Berger 1 , Marc Wygoda 1 , Ayman Salhab 1 , Marcel Fang 1 , Jon Feldman 1 , Aron Popovtzer 1