ESTRO 2026 Congress Report

By the ESTRO Focus group on Hyperthermia

Introduction

ESTRO 2026 marked an important milestone for the integration of hyperthermia (HT) within the ESTRO community. The ESTRO hyperthermia focus group celebrated its first anniversary, highlighting one year of intensified collaboration aimed at advancing clinical implementation, harmonisation, and research across Europe. For the first time, a dedicated HT journey was included in the scientific programme, reflecting the growing clinical, technical, and biological interest in this treatment modality. In addition, for the first time during ESTRO, an HT Meet & Greet was organised, attracting more than 45 participants, including radiation oncologists, medical physicists, RTTs and radiobiologists, demonstrating strong multidisciplinary engagement within the field.

Figure 1: Participants and members of the Hyperthermia Focus Group gathered during the Hyperthermia Meet & Greet at ESTRO 2026 to exchange knowledge, share experiences, and discuss future developments in hyperthermia.

Together, these developments underline the expansion of HT in modern radiation oncology and emphasise the increasing importance of structured collaboration, standardisation, and education to support its broader clinical adoption. These developments were reflected in a broad range of abstracts at ESTRO 2026, highlighting the expanding role of HT in oncology.

Clinical evidence

Across multiple studies, HT demonstrates consistent clinical benefit as an adjunct to radiotherapy (RT) and systemic therapies in both curative and palliative settings.

In recurrent breast cancer (Marina Arangüena Peñacoba, Spain), data from a prospective phase II study showed high treatment compliance of approximately 90%, with no ≥3 grade HT-related acute and late side effects and favourable survival outcomes, including a 6‑month recurrence-free survival rate of ~87%.

In gastrointestinal malignancies, HT combined with neoadjuvant chemoradiotherapy resulted in promising outcomes. In oesophageal cancer (Mau Shin Chi, Taiwan), pathological complete response (pCR) rates reached 62.5%, with 100% R0 resections and excellent local control at a median follow-up of 13.6 months. In rectal cancer (Laura Ferrera-Alayon, Spain), HT was feasible in both short- and long-course regimens, with 100% completion (≥50% sessions) in short-course treatment and 63.6% in long-course treatment, without grade ≥3 HT-related side effects and no delay in surgery.

In advanced and palliative settings, strong evidence was observed for bulky, treatment-refractory tumours. Deep HT combined with RT yielded partial volumetric response rates of up to 69%, with mean tumour reductions exceeding 50%, and symptom relief in 83% of patients experiencing pain (Neesen, Switzerland). Similar findings were reported in larger heterogeneous cohorts (n=57), where >90% treatment completion was achieved, and 74% of patients reported pain improvement, with local disease control observed in approximately 60% of evaluable patients (Martucci, Switzerland).

Early-phase clinical evidence in head and neck cancer (TANCA-I trial) confirmed feasibility, with successful completion of all planned HT sessions in initial patients (Tessa Coenraad, The Netherlands). No observed HT-related side effects, and effective heating reaching ~40°C in target regions.

Patient-reported outcomes further support these findings. In a real-world cohort of 118 patients, modulated electro-hyperthermia (mEHT) resulted in a statistically significant improvement in global quality of life (QoL) (+4.7 points; p=0.020), with clinically meaningful improvement in 35–50% of patients (Claudia Pedrero, Spain). Improvements were strongest in patients receiving systemic therapies, particularly mEHT combined with chemotherapy (+5.5 points) or immunotherapy (+17.8 points).

Biological and dosimetry insights

Several studies quantified the biological contribution of HT. Combined RT–HT modelling demonstrated additional dose effects of approximately 2.4–7.1 Gy EQD2, corresponding to increases in tumour control probability (TCP) of up to 75%, depending on temperature distribution (Carolina Carrapico Seabra, Portugal). Importantly, uncertainties in MRI thermometry resulted in only limited deviations (≤0.7 Gy EQD2 and ≤1.1% TCP), confirming the robustness of biological modelling.

These findings support the role of HT as an effective radiosensitiser, providing clinically relevant biological enhancement beyond physical dose delivery.

Treatment planning and technical developments

Advances in treatment planning significantly improve HT precision. Three-dimensional optimisation using HyperPlan® improved energy deposition in target volumes, with validation studies demonstrating excellent agreement with experimental data, including median relative errors of 0.9–4.6% across different applicators (Siddharth Arora, Germany and Anna Chiara Giovannelli, Germany).

Uncertainty analysis (Roel Kwakernaak, The Netherlands) revealed that dielectric tissue properties contributed the largest share to variability in thermal dose (mean ~47%), followed by patient positioning (~22%) and thermal tissue properties (~15%). Combined uncertainties resulted in temperature variability of approximately 2.4°C (95% CI) in T90, highlighting the need for robust patient-specific modelling.

Independent phase calculation tools demonstrated strong agreement with clinical planning systems, with mean phase differences of 2.5–5.4° and corresponding SAR deviations of approximately 2%, supporting their role in patient-specific QA (Frauchiger, Switzerland).

Quality assurance and harmonisation

Standardisation efforts are crucial for reliable HT delivery and multi-centre studies. A nationwide Dutch initiative successfully harmonised HT protocols for recurrent breast cancer, supporting the ongoing RT-HYPE trial (Lisca Wurfbain, The Netherlands).

Multi-centre QA studies confirmed compliance with established guidelines across all centres and demonstrated improved thermometry accuracy and stability following standardised calibration procedures (Abiram Kanagaratnam et al.). These studies identified probe orientation as a critical factor, with thermocouple misalignment (>15°) leading to measurable self-heating artefacts.

At the European level, HT implementation is expanding rapidly, with a 66% increase in active centres over the past five years and approximately 1,600 patients treated annually with combined HT+RT (Emanuel Stutz, Switzerland). However, key barriers persist, including limited reimbursement (~20% of centres), scepticism regarding efficacy (~18%), and high investment costs (~15%).

Patient positioning and device development

Improving patient comfort is essential for prolonged HT treatments. A newly developed immobilisation platform enabled 100% completion of 90‑minute sessions compared to 80% with a conventional MRI platform, while reducing discomfort scores (median 5.0 → 4.5) without significantly compromising positional accuracy (≤8–9 mm displacement) (Linnea Verbeek, The Netherlands).

Conclusion

HT is increasingly established as a valuable adjunct in radiation oncology, with consistent evidence supporting its feasibility, safety, and clinical benefit. Across studies, HT improves tumour response, symptom control, and quality of life without increasing side effects.

Advances in treatment planning, biological understanding and modelling, and QA are enhancing treatment precision, while harmonisation initiatives are enabling robust multi-centre evaluation. Future work should focus on prospective validation, translational studies, optimisation of patient-specific treatment strategies, and overcoming implementation barriers to support broader clinical integration.

We would like to thank all contributors to ESTRO 2026, including those presenting their work, participating in the focus group meetings and meet & greet sessions, and for their valuable presence. We look forward to continuing this momentum together at ESTRO 2027 in Milan!

Anton Rink, PhD student and specialised RTT, Department of Radiotherapy, Erasmus MC Cancer Institute, Rotterdam, the Netherlands.
Member of the ESTRO Focus Group on Hyperthermia

a.rink@erasmusmc.nl
Anton Rink - Erasmus MC | LinkedIn