Abstract

Filippo Alongi¹, Umberto Ricardi², Marta Scorsetti³, Lorenzo Livi⁴, Panagiotis Balermpas⁵, Yolande Lievens⁶, Pètra Braam⁷, Barbara Alicja Jereczek-Fossa⁸, Karin Stellamans⁹, Ivica Ratosa¹⁰, Joachim Widder¹¹, Heike Peulen¹², Piet Dirix¹³, Luc Verbeke¹⁴, Sara Ramella¹⁵, Hossein Hemmatazad¹⁶, Kaouthar Khanfir¹⁷, Xavier Geets,¹⁸, Paul Jeene¹⁹, Thomas Zilli²⁰, Beatrice Fournier²¹, Catherine Fortpied²², Felix Boakye Oppong²³, Piet Ost²⁴, Matthias Guckenberger²⁵

¹ IRCCS Sacro Cuore Don Calabria Hospital & University of Brescia, Advanced Radiation Oncology, Negrar (Verona), Italy; ²Università degli Studi di Torino, Torino, Italy, Radiation Oncology, Torino, Italy; ³Humanitas University, Department of Biomedical Sciences, Pieve Emanuele (Milan), Italy; ⁴Azienda Ospedaliero-Universitaria Careggi , Radiation Oncology, Florence, Italy; ⁵University Hospital Zürich, University of Zürich , Radiation Oncology, Zurich, Switzerland; ⁶Radiation Oncology Department, Ghent University Hospital and Ghent University, Radiation Oncology, Ghent, Belgium; ⁷Radboud University Medical Center Nijmegen, Radiation Oncology, Nijmengen, The Netherlands; ⁸European Institute of Oncology and University of Milan, Oncology and Hemato-oncology department, Milan, Italy; ⁹Campus Kennedylaan, AZ Groeninge Kortrijk , Kortrijk , Belgium; ¹⁰Istitute Of Oncology, Radiation Oncology, Ljubljana, Slovenia; ¹¹Universitaetsklinikum Wien, Radiation Oncology, Wien, Austria; ¹² Catharina Ziekenhuis, Radiation Oncology, Eindhoven, The Netherlands; ¹³ Iridium Network, Radiation Oncology,, Wilrijk , Belgium; ¹⁴ Onze-Lieve-Vrouw Ziekenhuis, Radiation Oncology, Aalst, Belgium; ¹⁵Policlinico Universitario Campus Bio-Medico- Oncology Center, Policlinico , Radiation Oncology, Roma, Italy; ¹⁶Bern University Hospital (Inselspital), Radiation Oncology, Bern, Switzerland; ¹⁷Hopital de Sion, Hopital du Valais , Radiation Oncology, Sion, Switzerland; ¹⁸ Cliniques Universitaires Saint-Luc, -, Brussels, Belgium; ¹⁹Radiotherapiegroep, -, Deventer, The Netherlands; ²⁰Hôpitaux universitaires de Genève - HUG - site de Cluse-Roseraie, , Radiation Oncology, Geneve, Switzerland; ²¹European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; ²² European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; ²³ (European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; ²⁴Iridium Network, Radiation Oncology, Wilrijk, Belgium; ²⁵University Hospital Zürich, University of Zürich, Radiation Oncology, Zürich, Switzerland

Several randomized phase II trials have reported improved outcome if local ablative therapies were added to standard-of-care treatment of oligometastatic cancer patients with very low rates of toxicity. In this analysis, based on the first patients included in the ongoing ESTRO/EORTC E²-RADIatE OligoCare cohort, we report on the early toxicity for patients treated with SBRT for oligometastatic cancer.

The analysis is based on a snapshot of the database on October 10th 2022 including only the first 1100 enrolled patients. A total of n=1002 were included in this analysis after exclusion of non-eligible patients or patients with incomplete data. The current update reports the patient characteristics and adverse events observed within 6 months of the start of SBRT, using the CTCAE v5 scale. Only events of grade 3 or higher related to radiotherapy are reported.

Patients were treated with SBRT at 32 centers across 9 European countries for oligometastatic breast (n=163), colorectal (n=183), non-small cell lung (n=198) or prostate cancer (n=458). The majority of patients had a good performance status (WHO 0-1: 82.4%). In 97% of cases, less than 4 metastases were irradiated, with most patients receiving radiotherapy for a single metastasis (67.2%). The most common organ sites irradiated were non-vertebral bones (22.9%), lung (20.8%), non-regional lymph nodes (18.3%) and spine lesions (15.8%). The median clinical target volume was 3.7cc (Q1-Q3: 1.2-12.8cc). The median number of fractions was 5 (range 1-11) with a median dose of 9.4 Gy per fraction (Q1-Q3: 7.5-12.2Gy). The median dose per fraction was highest for metastases from colorectal primaries at 13.1Gy per fraction, followed by NSCLC (10.2Gy), breast (8.6Gy) and prostate cancer (8.5Gy). The median BED, using an α/β of 10, delivered was 73 Gy (Q1-Q3 (59.7-104.4). SBRT was delivered in combination with systemic therapy in 38.3% of cases.
There were only 0.5% of patients with grade 3 or higher adverse events reported. In total 4 cases of grade 3 toxicity were reported (pain: 1, empyema: 1, pneumonia: 1, decreased appetite: 1) and 1 grade 5 toxicity (pneumonitis). In total, 6 patients (0.6%) were diagnosed with a new primary malignancy and 27 patients died (2.7%) within the first 6 months of follow-up.

Very few grade 3 or higher toxicity are being observed in the OligoCare cohort, with the vast majority of patients being alive at 6 months follow-up. Up-to-date data will be presented at the ESTRO congress.