ESTRO 2024 - Abstract Book

S5861

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

month period from 1 December 2020 to 27th July 2022. All patients were planned with IMRT or VMAT with RapidPlan™ in Eclipse (Varian Medical Systems, Palo Alto, CA).

This review split the patients into the various dose regimes, which included:

• 60 Gy in 20 fractions (n=87) – Prostate only. • 78 Gy in 39 fractions (n=298) – Prostate only (n=86), prostate bed only (n=44), prostate and nodes (n=135), prostate bed and nodes (n=33).

Results:

Through the inter-disciplinary discussion of shared planning there were key themes identified, which included:

• Various methods and staff understanding of how to use the RapidPlan™ model within the optimiser. • Requests for dosimetry change from Radiation Oncologists, despite published dosimetry clinical goals being met.

The plan metric review demonstrated that many of the benchmarks for OAR doses did not represent modern prostate planning expectations:

• In 95% of plans 60Gy prescriptions, 6 of the 8 plan metrics for rectum and bladder constraints were lower than the department goal by an absolute average of 12% (range 4-27%) • In 95% of plans 78Gy prescriptions to prostate only, 6 of the 8 plan metrics for rectum and bladder were lower than the department goal by an absolute average of 14% (range 2-25%) • In 95% of all prescriptions including nodal irradiation, all 8 plan metrics for rectum and bladder were lower than the department goal by an absolute average of 12% (range 3-28%) The attached table compares a selection of the departmental protocol objectives against observed plan metrics for bladder and rectum with prostate only plans. The table demonstrates a significant reduction in reported dose at the lower dose levels is a consistent theme for all prostate dosimetry planning and likely due to the superior performance of knowledge-based planning using modulated planning technology. Departmental protocols have now been amended and new goals were also added, including rectum V100%<1% and mean dose for bladder and rectum <50% of the prescribed dose.