ESTRO 2020 Abstract book

S1038 ESTRO 2020

(2), physicists (3), radiation therapy technologists (2), nurses (2), and radiation safety staff (3), all actively involved in these treatments, participated in the FMEA. A process map of our workflow was created, identifying major steps along with a list of failure modes (FM) for each step, yielding a total of 94 FMs for 23 steps. Each member of the team scored (1-10) each FM in each of the following categories: likelihood of occurrence (O), detectability (D), and severity (S), with 1 signifying the least likely to occur and easiest to detect, and the range [1-10] signifying the severity of dose delivery errors (wrong dose, acute toxicity, etc.) or, when applicable, the severity of radioactive contamination. The median values of O, S, and D were multiplied for each FM to obtain the risk priority number (RPN), with higher values indicating higher risk. Results The FM with the highest RPN (162) was the AA preparation. This had a high S due to its potential for significant nephrotoxicity and a high D due to it being nearly impossible to detect a failure in AA preparation. The next highest scoring FMs included failure to check the patient’s labs prior to treatment (140) (potentially leading to patient toxicities), failure to clarify release instructions to the patient (98) (potentially exposing other individuals to radiation), and failure to check the status of or prepare for patient incontinence (88) (potentially leading to major radioactive contamination). Most FMs, despite having high severity scores, were unlikely to occur and were easy to detect Conclusion With our current workflow, about 86% of the FMs identified in this FMEA were deemed to be easily detectable (D≤3) and have low occurrence rates (O≤3). However, our FMEA revealed that additional checks/steps were needed to limit the potential for dose delivery errors and radioactive contamination, requiring modifications of our procedures. We encourage others to evaluate their workflows similarly using FMEA to mitigate the risks and increase the safety of this effective, yet resource- and time-intensive, PRRT. PO-1771 Significant lower dose to brain after implementation of new treatment protocol for brain metastasis A. Haraldsson 1 , J. Engleson 2 , E. Wieslander 1 , P. Engström 1 , A. Abri 2 , M.A.R. Per 2 1 Skåne University Hospital, Radiation Physics- Department of Hematology- Oncology and Radiation Physics, Lund, Sweden ; 2 Skåne University Hospital, Department of Hematology- Oncology and Radiation Physics, Lund, Sweden Purpose or Objective Recently, a new radiotherapy treatment protocol for stereotactic brain metastasis was implemented at our clinic. The protocol included new constraints to the volume of normal brain receiving more than18 Gy, V 18Gy , and a change from homogeneous to inhomogeneous dose distribution in the planning target volume (PTV). The implementation was based on a study(ies) that found a correlation between V 18Gy and brain necrosis, Minniti et al. 2016. The aim of this study was to examine any difference in dose to the brain for patients treated prior and after the implementation of the new protocol. Material and Methods A total of 127 volumetric modulated arc therapy (VMAT) and helical treatment plans was retrospectively analysed and selected in reversed chronological order. The VMAT plans were optimized using 2-3 arcs, with at least one non- coplanar arc. Prior to the new protocol, the dose was 30 Gy in 3 fractions prescribed as mean dose to PTV and the aims for the dose distribution were high conformity and homogeneity. With the new protocol, dose prescription was changed to 30 Gy in 3 fractions to 95% of the PTV and

e2e protocol validation – The e2e protocol was tested in two centers following provided instructions and devices. Results are presented in table 1.

Conclusion SBRT performed using local devices and expertise has been proposed and preliminary tested to demonstrate the feasibility of the entire procedure. This is an interesting result aiming to propose a possible solution to those Italian centres interested to verify SBRT treatments’ accuracy and deliverability in moving phantom. [1] Pallotta S, et al. ADAM: A breathing phantom for lung SBRT quality assurance. Phys Medica 2017. [2] Pallotta S, et al. ADAM phantom to test 4D medical imaging and dose delivery devices. Phys Med Biol 2019. [3] Marrazzo L, et al. GafChromic®EBT3 films for patient specific IMRT QA using a multichannel approach. Phys Medica 2015. PO-1770 Failure Modes and Effects Analysis with Lu- 177 Dotatate PRRT in a Radiation Oncology-based Program N. Maughan 1 , H. Kim 1 , M. Roach 2 , J. Garcia-Ramirez 1 , M. Amurao 3 , Y. Hao 1 , J. Zoberi 1 1 Washington University in St. Louis, Radiation Oncology, St. Louis, USA ; 2 Hawai’i Pacific Health, Radiation Oncology, Honolulu, USA ; 3 Washington University in St. Louis, Radiation Safety, St. Louis, USA Purpose or Objective Lutetium-177 ( 177 Lu) Dotatate is a peptide receptor radiotherapy (PRRT) used to treat neuroendocrine tumors in the midgut. The administration of this PRRT is technically and logistically challenging, with concomitant infusion of amino acids (AA) over the course of several hours to protect the kidneys and a primary excretion route through the urine, which poses significant radiation safety concerns. After implementing and establishing this therapy in our Radiation Oncology center, we performed a failure modes and effects analysis (FMEA) to assess and improve the robustness of our clinical workflow. Material and Methods We developed a detailed clinical workflow that includes treatment area preparation for contamination control, administering the AA and PRRT with a checklist, and treatment area decontamination. A team of physicians