ESTRO 2025 Congress report

This report provides a summary of presentations made during ESTRO 2025 that were dedicated to skin cancer and soft-tissue sarcoma (STS).

Of all 220 sessions at ESTRO 2025, three were dedicated to skin cancer and four to STS. The three symposia on skin cancer comprised eleven oral presentations, nine mini-oral presentations, and forty-one posters. The four sessions focusing on STS comprised two proffered paper presentations, three panel discussions, 31 posters, and three mini-oral presentations.

Soft tissue sarcomas

A key panel discussion featuring Rick Haas, Mateusz Spalek, and Silvia Stacchiotti, moderated by Nicolaus Andratschke, revisited the long-standing debate on preoperative vs. postoperative radiotherapy in soft tissue sarcoma. The panel reaffirmed preoperative radiotherapy as the standard of care, citing randomized evidence and emphasizing benefits such as lower doses, smaller target volumes, better tumor visualization, possibly improving resectability, reduced late toxicities, and potential for both pathological response assessment post-surgery and radiological response assessment. The latter was supported by single-institutional data (Cammelli et al., ePoster) showing a median tumor volume reduction of 12.5% after neoadjuvant radiotherapy.

 

Updates on preoperative hypofractionation for extremity and trunk wall STS were also discussed. Multiple phase II trials—ranging from ultra-hypofractionation (5x5 Gy to 5x8 Gy) to moderate hypofractionation (15x2.85 Gy)—have shown comparable local control to conventional regimens. However, due to the absence of randomized data, hypofractionation remains experimental. It was commonly used during the COVID-19 pandemic, demonstrating feasibility. The ongoing Dutch SCOPES trial (14x3 Gy vs. 25x2 Gy), led by Rick Haas, is the first randomized comparison and will report initial results in late 2025 or early 2026. The panel agreed that while 5x8 Gy (Kalbasi et al.) caused unacceptable toxicity (16% amputations), 5x5 Gy (Spalek et al.) may be insufficient for most histologies except myxoid liposarcoma. Future studies may explore shorter but safe regimens between these extremes.

Another major highlight was the SU2C-SARC032 trial (Mowery et al., Lancet, 2024), the first randomized study to show a 15% improvement in disease-free survival with pembrolizumab added to preoperative radiotherapy for undifferentiated pleomorphic sarcoma and dedifferentiated liposarcoma. While hailed as a milestone, the panel emphasized the need for further trials to identify the most responsive subgroups and confirm overall survival benefit before adopting it as standard care.

 

Preliminary findings from the ongoing single-arm phase II SPRING trial (Greto et al.) investigating a preoperative simultaneous integrated boost radiotherapy regimen for extremity and trunk wall STS—25×2.4 Gy to the resection plane interface and 25×2 Gy to the tumor volume and surrounding at-risk tissue—have shown a 100% R0 resection rate in the first 15 patients. These results further support the rationale for preoperative radiotherapy in STS. Final outcomes are eagerly awaited.

Thought-provoking data was presented by Barnes et al. showing that over the last nine years sarcoma abstracts only comprised 0.88% of all submitted abstracts underlining a clear underrepresentation and the need for more independent sarcoma-related topics and sessions. Sarcomas are rare cancers and collaboration fostered through international conferences, such as ESTRO, are key to drive research forward and should therefore be further represented.

Skin cancer

David Moreno Ramirez, Professor of Dermatology and MOHs Specialist, Spain and Peter Kölblinger, Dermato-Oncologist, Austria, opened the 2^nd Joint ESTRO-EADO Symposium: “Behind local control: Modern integrated opportunities in the management of non-melanoma skin cancer.” Kölblinger, along with Ramirez succinctly described the future of skin cancer treatment as “treat together, and treat early.” The spectrum of skin cancers are vast. The increasing incidence, higher ultra-violet exposure, ageing population with competing risks, along with increasing disease complexity, skin cancers benefit from multi-professional working and tumour board approach, as both are required to treat this complex patient group.

Kölblinger reported quality of life metrics following skin cancer treatments, with evidence supporting that nothing less than curative treatment is needed to improve patient well-being. Paul Martin Putora, Switzerland, Radiation Oncologist and Methodologist, presented decision-making trees in non-melanoma skin cancer (NMSC). Twenty-two ESTRO-nominated experts in skin radiation therapy formulated decision trees detailing their recommendation for post-operative radiotherapy. There is a wide range of decision-making criteria in clinical use, with significant discrepancies in treatment recommendations and delivered dose-fractionation schedules. Putora described eight common decision-making criteria with all experts delivering post-operative radiation therapy for close or positive pathological margins. Brigham and Women's Hospital (BWH) staging are favoured and provide the best prognostication and correlation with clinical outcomes; the United Kingdom SCC-After Trial is in accrual and examines the role of post-operative radiation therapy for BWH T2b/T3 cutaneous squamous cell carcinoma which have been completely excised.

Jesper Eriksen, Denmark, presented initial outcomes from the Danish NMSC radiation therapy database. This 2019-2023 registry study detailed the cosmetic outcomes of 337 patients to 6-months following radiation therapy based on a subjective four-point likert scale. Of the 157 evaluable patients, 93% were “very satisfied” with their cosmetic result; the data matched clinician views and further work is commissioned for a 3-year project focussing on cosmesis and recurrence.

Emma Connolly, Australia, detailed the prognostic subgroups from the TROG 05.01 POST Trial. Extra-capsular extension and/or lymph node diameter ³ 22mm deems the patient at twice the risk of recurrence and at triple the risk of death: DFS HR 2.0 (CI 1.3-3.1 p=0.001). These POST Trial parameters define eligibility for the recently reported C-POST Trial, with impressive 24-month disease-free survival 87.1% versus 64.1% with the addition of 12-months cemiplimab following post-operative radiotherapy.

Kurian Joseph, Canada, reported outcomes of 949 Merkel cell carcinoma patients with or without lymph node irradiation between 1982-2015. 78% were early stage I/II and despite the intrinsic cohort heterogeneity, those early-stage patients who received lymph node basin radiation therapy had lower rates of recurrence 16% versus 40% p=0.001 at median follow up 27 months. Collating data in a rare tumour type is a significant feat. Modern guidance supports whole body FDG PET-CT staging and sentinel lymph node biopsy in the absence of FDG PET-CT avidity.

Forty-one skin cancer posters were selected for presentation at ESTRO 2025 including novel 3D printing solutions for electron lead mask and brachytherapy moulds, stereotactic radiosurgery in melanoma brain metastases, hyperthermia, and radio-immunotherapy combinations.

Mateusz Spałek and Marcin Miszczyk, along with Skin and Soft Tissue Focus Group Chairs, Agata Rembielak and Beate Timmerman and Focus Group Secretary Romaana Mir conducted the first ESTRO “Meet and Greet” session. We welcomed engagement from fellow conference attendees, showcased active work from this Focus Group, and highlighted clinical areas for development.

Dr Romaana Mir, MB ChB MSc FRCP FRCR MD(Res)

Mount Vernon Cancer Centre

Northwood, UK

Secretary, ESTRO skin and soft tissue focus group

romaana.mir@nhs.net
LinkedIn: Romaana Mir

Dr Siyer Roohani, MD

Department of Radiation Oncology

Charité - University Medicine Berlin and Berlin Institute of Health

Berlin, Germany

siyer.roohani@charite.de

LinkedIn: Siyer Roohani

X: @SiyerRoohani