S1531
Interdisciplinary - Quality assurance and risk management
ESTRO 2026
Radiotherapy department, Fundación Arturo Lopez Perez, Santiago, Chile
The decision to resume treatments was based on balancing the inherent risks of manual spreadsheet- based verification with the clinical urgency indicated by the radiation oncologists. Initial treatments were delivered without the OIS, followed by a meticulous review of patient data, including remaining fractions, doses, and monitor units. A structured restoration process enabled a phased return to electronic operations within 13 days, at which point new simulations were safely resumed. However, full connectivity was not restored until 23 days after Day 0. The timeline during the process is shown in Figure2.
Purpose/Objective: To describe the coordinated and successful contingency plan execution following a critical cyberattack incident that compromised the entire hospital network in a multi-vendor radiotherapy department in Chile, focusing on minimizing treatment interruption and ensuring patient safety. Material/Methods: A case report was conducted following a ransomware attack that affected multiple platforms, including treatment planning systems (TPS) such as Eclipse (Varian), Precision (Accuray), and Oncentra (Elekta), as well as secondary dose verification and quality assurance softwares. The radiation oncology information system Mosaiq (ROIS Elekta) was connected to five linear accelerators — one Synergy, two Halcyons, one CyberKnife, one Radixact — and an Elekta brachytherapy suite, as well as a Somatom (Siemens) CT simulator. At the time of the attack 132 patients were under treatment across all modalities. In order to mitigate any further encryption into machine consoles, a clinical downtime policy (CDP) was activated and a multidisciplinary incident response team (IRT) was organized comprising informatics, medical physics, radiation oncologists, therapists and radiation protection officer. The IRT's primary tasks were to triage patients, implement manual chart checks using hardcopy backups, and collaborate with multiple vendors to systematically restore and validate systems while ensuring data
Conclusion: A severe cyberattack poses a real threat to radiation oncology centers. The success response was directly attributable to activating an IRT and implementing a comprehensive CDP. Effective preparedness in a multi- vendor setting requires not only technological defenses but also human-centered, multidisciplinary protocols and resilient clinical operation under severe conditions. Keywords: ransomware, radiotherapy, cyberattack Digital Poster 3634 Comparative evaluation of ABC- and SGRT-based DIBH techniques for left-sided breast radiotherapy: correlation of setup accuracy and in- vivo dosimetry Ali Abdelaziz Eid, Mahmoud Meselhy Ahmed, Ramanathan Viswanathan, Zainab AbdulRazzaq Alhaddad radiation oncology, Bahrain Oncology Centre, Manama, Bahrain Purpose/Objective: To evaluate and compare the geometric accuracy, dosimetric stability, and in vivo verification of Active Breathing Coordinator (ABC) and Surface-Guided Radiotherapy (SGRT) techniques—used independently or combined—for Deep Inspiration Breath Hold (DIBH) in left-sided breast radiotherapy, focusing on 6D
integrity. Results:
As part of the contingency plan, all systems were shut down, preventing further encryption from reaching the treatment delivery units. Following a comprehensive assessment of the RT servers, and as a safety measure, it was decided to reinstall the entire environment. Despite the additional workload and manpower required, the institution chose not to cooperate or negotiate with the attackers. Figure 1 illustrates a simplified diagram of the platforms and interfaces involved.
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