1121 - Impact of a Prospective Institutional Peer-Review Program in standardization of Target Delineation and Planning Variability in Radiotherapy
Presenter(s)
L. D. Faroni1, B. Souza2, F. Barreto2, L. Martins3, L. Pedro2, L. Almeida2, M. C. Rosa3, J. X. Filho2, F. Y. Y. Moraes4, and R. Serrano2; 1D'Or Oncology Center, Rio de Janeiro, Brazil, 2Oncologia D'Or, Rio de Janeiro, Brazil, 3Oncologia D’Or, Rio de Janeiro, Brazil, 4Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
Purpose/Objective(s): Inter-clinician variability in target volume delineation, dose prescription, and treatment planning remains a major source of heterogeneity in radiotherapy delivery, even within institutions with established protocols. We evaluated the longitudinal impact of a structured, prospective peer-review program on standardization of contouring, planning, and fractionation practices in a multisite private radiotherapy network.
Materials/Methods: All consecutive radiotherapy plans presented for prospective peer review between March 2020 and October 2025 were included. The institution comprised four sites, six linear accelerators (3 TrueBeam®, 2 Trilogy®, 1 Clinac 600C®), and a multidisciplinary team of 10 radiation oncologists, 10 physicists, and 3 dosimetrists. Daily peer-review conferences required participation of =50% of the clinical team prior to treatment approval. A structured dataset captured primary tumor site, target volumes, prescribed dose and fractionation, number of isocenters, technique, treating oncologist, consensus status, and need for modification. Primary endpoint was the proportion of cases requiring modification after peer review; secondary endpoints included drivers of revision, temporal trends in contouring and fractionation, and site-specific standardization (breast as index disease).
Results: A total of 12,839 treatment plans were reviewed. In the first three months of implementation, 13.6% of cases required modification; this decreased to 6.5% by the end of 2020 and to 1.4% in 2025, demonstrating sustained process standardization over time. Across 2020, 103 plans were modified, most commonly due to physics planning standardization (35%), dose/fractionation adjustments (16%), and contour revisions (15%). Breast cancer represented the most frequently reviewed site for contouring and prescription alignment. Hypofractionation adoption increased progressively, with the mean number of fractions per treatment declining from 13.7 in 2020 to 11.2 in 2025. For breast radiotherapy, fractionation practice in 2020 was heterogeneous (40 Gy/15 fractions: 49%; 50 Gy/25 fractions: 43%; 26 Gy/5 fractions: 8%), whereas by 2025, near-complete convergence toward standardized regimens was observed, with only one patient treated with 50 Gy/25 fractions and uniform planning approaches across sites.
Conclusion: Implementation of a mandatory, prospective peer-review workflow across a multisite radiotherapy network was associated with a marked and sustained reduction in contouring, planning, and prescription variability. The program accelerated adoption of hypofractionated regimens and standardized technical execution, reinforcing peer review as a scalable quality-assurance strategy with potential to improve treatment consistency and downstream clinical outcomes.