ESTRO 2021 Abstract Book

S272

ESTRO 2021

issues encountered and lessons learnt during this pandemic will help us prepare for future pandemics . This presentation will focus on the RTT committee guidelines and the results of the survey and how we can use these in the future. RTTs are front line health care workers and should be recognized as such in all countries.

SP-0371 Radiotherapy service continuity during the COVID-19 pandemic P. Scherer 1 1 County Hospital Salzburg, University Clinic for Radiotherapy and Radiooncology of the Paracelsus Medical University, Salzburg, Austria Abstract Text The COVID-19 (SARS-CoV-2) pandemic has a great impact on our lives in nearly every aspect ever since early 2020. Restrictions and the impact of the pandemic also affects the health care systems and changed with the numbers of infections in each respective area, region or state… with the continuity of health care services being one of the mayor concerns. Not only units directly linked to the care for SARS-CoV-2 patients were impacted but the whole health care service. In regard to radiotherapy service several aspects had to be weighted to ensure safe continuity of cancer therapy for patients and staff. These included adequate PPE which especially in the early phases proofed to be in short supply across many countries. Furthermore, safety measurements were issued and special concepts were created to lower the risk of infections in the hospital. On the one hand, these were enacted to secure our cancer patients and colleagues but on the other hand also to ensure availability of sufficient numbers of staff to secure adequate continuity of service respectively. Among these concepts several different strategies evolved including the use of home office where possible, creating split teams and changed formats for team meetings but also the wider use of hypofractionation and attempts to reduce the number of patients in the waiting areas to ensure safe distance and several others… Additionally, separated waiting areas or treatment time slots for infected patients as well as patients with suspected infection were established in several institutes to allow treatment of these patients when a delay of the treatment was no option. Furthermore, several governments enacted mandatory regular testing for health care workers, prohibited traveling and among other health care workers prioritized those working with cancer patients in their vaccination programs. However, with the ongoing impact of the pandemic and the respective restrictions further issues arise. In some cases, patients did not seek health care or had to suffer prolonged waiting times for diagnostic scans or therapy and now enter radiotherapy departments with somewhat more advanced stages of cancer. Furthermore, the lack of social contacts and restrictions regarding activities have a huge effect on stress levels. Unattended, this could pose a challenge because compensation/recreation strategies of health care workers are impeded in a time in which these are confronted with additional pressure. Continuous education is also affected, with CPD options being delayed or reorganized into online formats but often lacked networking possibilities. Additionally, media reports and changing guidelines and restrictions produce a constant stress level. Last but not least vaccination programs are often not proceeding as fast as might be desired and the effectiveness of the vaccinations could be impaired by mutations of the virus. In summary service continuity was provided with somehow manageable impact on the radiotherapy service, but the ongoing impact of the pandemic puts further pressure on the health care systems and radiotherapy service and especially on each and every staff member rises. We have to address these issues to ensure continuous and safe radiotherapy for our patients but also to keep ourselves and our colleagues safe and healthy. SP-0372 Advancement of model-based dose calculation algorithms in brachytherapy and their clinical impact J. Vijande 1 1 University of Valencia, Atomic, molecular, and nuclear physics department, Valencia, Spain Abstract Text The evaluation of the absorbed dose deposited on a patient following a pre-ordained clinical plan has undergone a renaissance during the last decade. The combined role played by increasingly powerful computational architectures together with new refined algorithms allows the clinical user to reach an accuracy only dreamed of during the last decades. Among the different radiation modalities, it is probably brachytherapy the one that has evolved more drastically in the last few years. Absorbed dose in clinical brachytherapy have been reported since 1994 by means of the well-known TG-43 formalism. However, such approach requires dose kernels obtained by means of Monte Carlo (MC) simulations assuming that the patient is made of water and immersed in an infinite volume of water. Therefore, effects like interseed attenuation, tissue heterogeneities, patient geometry or applicator materials are not explicitly considered when creating a clinical plan. Fortunately, in the last years, new Model Based Dose Calculation Algorithms (MBDCAs) have been developed. In 2012, AAPM, ESTRO, ABS, and ABG released a report, TG-186, to provide guidance for early adopters of MBDCAs for brachytherapy, and to ensure clinical practice uniformity. TG186 goes one-step further, defining MC as the gold standard to which any new dose calculation algorithms should be compared and commissioned. Therefore, any MBDCA algorithm has to be verified against state-of-the-art MC calculations to ensure: i) that it reproduces correctly the “true” absorbed dose as described by MC, ii) to evaluate possible discrepancies due to the unavoidable numerical approximations required, and iii) to guide the clinical user when moving away from the current TG-43 clinical planning. It is evident that performing such complex numerical simulations is so time consuming and demanding that, in practice, it is usually beyond the capabilities of a regular clinical environment. This is the main reason why Symposium: Next generation of brachytherapy treatment planning systems: What do we want and what do they need?