ESTRO 2024 - Abstract Book

S1966

Clinical - Mixed sites, palliation

ESTRO 2024

1 Iridium Network, Radiation oncology, Ghent, Belgium. 2 Ghent University, Human structure and repair, Ghent, Belgium. 3 EORTC, EORTC, Brussels, Belgium. 4 IRCCS Sacro Cuore Don Calabria, Radiation oncology, Verona, Italy. 5 RadboudUMC, Radiation oncology, Nijmegen, Belgium. 6 Ghent University Hospital, Radiation oncology, Ghent, Belgium. 7 Wien University, Radiation oncology, Vienna, Austria. 8 UMC Utrecht, Division of Imaging and Oncology, Utrecht, Netherlands. 9 King's College London, Centre for Cancer, Society, and Public Health, London, United Kingdom. 10 University Hospital Zurich, Radiation oncology, Zurich, Switzerland

Purpose/Objective:

OligoCare is a cohort of the ESTRO-EORTC radiotherapy observational platform, E2-RADIatE (https://project.eortc.org/e2-radiate/), which evaluates SBRT in oligometastatic breast, colorectal, non-small cell lung and prostate cancer patients [1]. We here describe the methodology to compare single-fraction vs multiple-fraction SBRT in oligometastatic cancer patients using a Trials within Cohorts (TwiCs) approach within the OligoCare project.

Material/Methods:

E2R uniquely allows for embedding randomized research questions to determine whether an approach is superior or equivalent to another. The few eligibility criteria, the simplicity of the informed consent, and the request for standard of care data facilitates patient accrual and also provides a ready-made pool of standard comparator arms for use in randomized studies. Using the TwiCs approach, patients can be randomized to receive multiple fraction SBRT (standard of care) or one fraction SBRT (experimental treatment). Patients who will be randomized to receive single-fraction SBRT will need to consent to receiving the experimental treatment.

Results:

Over 2,000 patients have been enrolled into OligoCare so far. Most TwiCs designs in oncology have been limited to national cohorts [2] and we here aim to expand this on an international scale. However, there are challenges with onboarding 55 sites from 12 different European countries. TwiCs and two-stage consents are a relatively new concept in many European countries. Their use must be carefully explained, and special effort into educating Ethics Committees must be carried out with the support of local PIs. A balanced approach guiding safe practice of especially single-fraction SBRT is warranted, without narrowing the institutional SBRT practice within the non interventional nature of the E2R project.