Important new results from EORTC presented at ESTRO Congress 2025

Radiation oncology is among the main pillars of the EORTC scientific strategy and plays a vital part in its mission to improve clinical research through multidisciplinary partnerships. The annual ESTRO congress provides an opportunity for radiation oncologists to present results from EORTC studies that advance radiotherapy (RT) treatment and provide benefits for patients. At this year’s congress, held in Vienna from 2 May to 6 May, EORTC researchers once again presented important results.

Joint ESTRO-EORTC on novel methodologies for clinical research in radiation oncology: Time to think outside of the box?

On Sunday 4 May (08:45 – 10:00), we will hold a joint session with ESTRO exploring innovative approaches to clinical research in radiation oncology, challenging traditional methodologies and highlighting the need for adaptability in a rapidly evolving field. From EORTC, Felix Oppong and Mieke Van Hemelrijck will respectively present the challenges around pragmatic clinical trials ¹ and Trials within Cohorts (TWICs). ²

Additionally, Enrico Clementel will speak about “Bringing the Next Generation Forward – The Leadership Perspective” in an engaging session on the need to support the next generation of professionals in oncology and radiotherapy (Monday 5 May, 10:30 – 11:30). ³

Radiation oncology and real-world data: E²-RADIatE

The E²-RADIatE initiative was set up in 2019 by EORTC and ESTRO to encourage pan-European collaboration in radiation oncology (RO). It aims to generate robust data on RO’s role in cancer treatment and to further develop the discipline into therapeutic strategies. In her presentation ⁴ at ESTRO 2025, Professor Yolande Lievens will discuss how the collection of real-world evidence (RWE) can help improve RO practices across Europe. RWE is being used increasingly to study treatments in patients who are more representative of the general population, in addition to the carefully selected population involved in clinical trials.

OligoCare, the first cohort, opened in June 2019 and evaluates radical metastasis-directed radiotherapy in oligometastatic (OMD) patients with breast, lung, prostate or colorectal cancer. With 58 centres active, 3025 patients were included. Initial publications illustrated that in stereotactic body radiotherapy (SBRT) – a type of radiation therapy that uses high fraction doses to deliver very precise radiation to a target – the doses vary by primary cancer and oligometastatic location, higher doses being delivered to lung and liver lesions; that acute grade ≥3 SBRT-related toxicity is limited to 0.5% within 6 months, thus confirming the safety of SBRT in the real-life management of OMD and that quality-of-life remains unaffected 6 months after SBRT for OMD in prostate cancer. The overall survival analysis is ongoing.

A second cohort, ReCare, began in June 2023 with 310 patients enrolled in 14 centres. This data collection examines the increasingly important relevance of re-irradiation. And a third, AlphaCare, is in development and will investigate the toxicity of combining novel drugs with high-dose radiotherapy.

“Results from E²-RADIatE have already shown how that RWE collection can clarify radiotherapy practices across Europe, complementing randomised trials, generate new hypotheses and advance research implementing innovative trial methodologies,” says Prof Lievens. “The collaboration paves the way for additional research questions and supports innovation in radiotherapy.”

Stereotactic Body Radiation Therapy – getting the dose right

Stereotactic Body Radiation Therapy (SBRT) delivers extremely precise, very intense doses of radiation to cancer cells while minimising damage to healthy tissue. SBRT involves the use of sophisticated image guidance that pinpoints the exact three-dimensional location of a tumour so that the radiation can be more precisely delivered to cancer cells.

In addition to the definition of the target area to be treated, the dose to be delivered must be precisely calculated. While the dose is usually prescribed to the planning target volume (PTV), this can lead to significant variations in the dose that is delivered, and particularly in non-homogeneous tissue such as that of the lung. Volha Hertsyk, MSc, presented preliminary results from a study ⁵ investigating the differences in dose distribution within the GTV in lung cancer patients receiving SBRT using the dose prescribed to the PTV.

The researchers collected data from four relevant EORTC studies, and examined the prescribed PTV dose, mean GTV dose, the dose calculation algorithm, and the target locations. They were able to identify a total of 232 lung lesions from 167 patients that had sufficient data for analysis. They then analysed the relative dose difference between the prescription dose and the mean GTV dose in each study.

“We found significant variability in GTV dose distribution when using PTV for dose distribution in lung SBRT,” said Ms Hertsyk. “We believe that our findings support a shift towards using a direct GTC-based prescription approach, which could help reduce discrepancy in dose reporting, enhance treatment precision, and provide a more accurate reflection of dose delivery within the tumour.”

Brain metastases in small cell lung cancer – improving patients’ quality of life

Small cell lung cancer (SCLC) is characterised by a rapid tumour doubling time and the swift development of metastases, including in the brain. To evaluate active brain MRI surveillance in SCLC patients, the EORTC PRIMALung randomised phase III trial compares brain MRI surveillance alone (the experimental arm) to brain MRI surveillance combined with PCI (the control arm) in patients with any stage SCLC. Patients in the control arm may be treated with hippocampal avoidance prophylactic cranial irradiation (HA-PCI) which is known to prevent cognitive decline. A poster presentation ⁶ by Dr Luiza Souza described the dosimetric assessment of the target hippocampi and peri-hippocampal regions of 21 patients treated with HA-PCI in this study and also focused on reporting compliance with the protocol. The researchers were able to show that HA-PCI with a radiation dose of 25Gy given in 10 fractions was both feasible and consistently deliverable, in all cases at 8 mm from the hippocampi, thus helping to avoid memory loss and other symptoms of cognitive decline that have an important impact on patients’ quality of life.

New trial will study the combination of highly-directed radiotherapy and immunotherapy in patients with cancer of the mouth, throat or larynx

Another poster introduced the randomised Phase III EORTC 2014-HNCG PROLoNg trial ⁷ of Pembrolizumab and radiotherapy for oligometastatic ^a squamous cell carcinoma of the head and neck. The trial will be launched this year in Belgium, Italy, Spain, and Switzerland, and will be the first multicentric, international effort aiming to provide high level evidence for the combined approach of stereotactic ablative radiotherapy (SABR – a highly directed form of radiotherapy that delivers a high dose to the tumour while sparing surrounding healthy tissues) and immune checkpoint inhibitors ^b for oligometastatic squamous cell carcinomas of the head and neck.

Dr Denis Lacombe, EORTC CEO, said: “Radiation oncology plays a major part in providing high-quality patient care. EORTC is committed to moving forward in RO research, which we see as an essential tool in our mission to provide the best treatment for every cancer patient.”

New guidelines for RO treatment of rare pediatric cancer

EORTC RTQA capabilities extend their support to the research activities of the European Society for Paediatric Oncology (SIOPE), the progress of which will also be highlighted in another presentation⁸ at ESTRO Congress by Dr Maria Chiara Lo Greco.

It will describe the development of new consensus guidelines for defining the clinical target volume for whole abdominopelvic radiotherapy (WAP-RT). WAP-RT is a complex treatment used for rare types of paediatric sarcoma that have metastasised to the peritoneum, the membrane lining the abdominal cavity. Due to the rarity of WAP-RT indications in paediatric oncology, achieving consistency in target volume delineation can be particularly challenging.

The researchers reviewed all patients enrolled in the Frontline and Relapsed Rhabdomyosarcoma (FaR-RMS) trial undergoing WAP-RT, to identify and address areas of variation. As treatment volume encompasses a large anatomical region, delineating the precise area to be treated is very important to improve local control and reduce the exposure of surrounding healthy tissues to radiation, hence the need for detailed, highly accurate guidelines for its definition.

“Paediatric sarcomas with peritoneal involvement are rare and their treatment is very challenging. We need large-scale international co-operations such as the SIOPe/EORTC initiative QUARTET, to be able to improve consistency and obtain more robust results,” said Dr Lo Greco. “We will be further validating the new guidelines through prospective monitoring of WAP-RT cases in FaR-RMS before adopting them in future trials.”

^a A type of metastasis in which cancer cells from the primary tumour travel through the body and form a small number of new tumours in one or two other parts of the body. This limited spread means that there is still a potential for cure, whereas this is seldom the case in tumours that have metastasised more widely.
^b Drugs that prevent the immune system from switching off and help it to find and attack cancer cells.

¹ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/59/ 
² https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/58/
³ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/96/
⁴ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/2397/
⁵ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/1361/
⁶ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/3636/
⁷ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/1062/
⁸ https://user-swndwmf.cld.bz/ESTRO-2025-Abstract-Book/1626/