Room: Track 6
Purpose: stereotactic body radiotherapy (SBRT) involves risk of severe complications due to high dose per fraction, organs at risk in high dose gradient and frailty of patients. We evaluated the safety of the departmental paraspinal SBRT program by applying failure modes and effects analysis (FMEA).
Methods: analysis was conducted by a multidisciplinary committee (2 therapists, 1 dosimetrist, 3 physicists,2 radiation oncologists). The paraspinal program was segmented into three phases (simulation, treatment planning, and delivery; each phase was further divided into a sequence of processes. The committee identified failure modes (FM) from each process. Each FM was scored in terms of occurrence, severity and detectability (Ford et al., IJROBP 2019), and the product of the three parameters, the risk probability number (RPN). Machine FMs were evaluated separately.
Results: paraspinal program was characterized as a sequence of 8 simulation, 15 treatment planning, and 12 treatment delivery processes. A total of 18/29/18/8 FMs were identified from simulation, planning, treatment, and machine failure, respectively. The average RPN was 66.9/96.7/65.5/44.5 for simulation, planning, treatment, and machine failure, respectively. The FMs with the highest RPN were: “incorrect immobilization requiring a new mold” (RPN:117.3) for simulation, “previous radiotherapy outside the institution incorrectly evaluated by a planner” (293.3) for treatment planning, “ExacTrac reference image taken after a patient has moved” (217.8) for delivery. The second highest RPN of all FM was “incorrect registration between diagnostic MRI and planning CT” (273). In comparison, the machine FM with the highest RPN was “6 MV flattening-filter free beam steering error” (160.0)
Conclusion: on the institutional FMEA, we identified needs to improve our policies on previous treatment evaluation and timing of the ExacTrac reference image. Furthermore, MRI-only planning could eliminate 4 FMs pertaining to fusion error and myelogram CT, and improve the safety of paraspinal SBRT.