Lessons learned from implementing a transit dosimetry program: impact on patient safety

PURPOSE: Safety and quality assurance software in external beam radiotherapy may improve oncologic outcomes by enabling early detection of treatment delivery deviations. This work describes the clinical implementation of an automated in‑vivo transit dosimetry (IVTD) program and evaluates its role as a patient safety barrier. MATERIALS AND METHODS: An automated IVTD program based on PerFRACTION™ was progressively integrated into clinical practice over five years. A total of 11,821 treatment plans were analyzed with PerFRACTION™ (7,424 with IVTD), comprising 140,759 fractions. Measured and expected transit dose distributions were compared using treatment site‑specific gamma criteria and tolerances. Fractions failing tolerance triggered alerts that were investigated to identify causes and assess clinical impact. Events potentially affecting patient safety were reported in the institutional incident reporting and learning system (IRLS), while anatomical changes supported adaptive radiotherapy. RESULTS: Of all fractions, 16.4% triggered alerts, approximately half false positives and 8.0% true deviations. The highest failure rates were observed in esophageal (47%) and colorectal (34%) treatments, and the lowest in pelvis (6%) and prostate (3%), considering site-specific tolerances. IVTD supported adaptive radiotherapy, triggering 37%, 30%, and 27% of replanned cases in head‑and‑neck, breast, and lung treatments, respectively. Of 803 incidents reported in the IRLS, 34 involved incorrect fraction delivery, and 12 were detected by IVTD, with representative cases presented. CONCLUSIONS: Daily IVTD use over five years contributed to detecting patient safety events, acting as an additional safety barrier. It also supported adaptive radiotherapy, particularly in lung, breast, and head-and-neck treatments.