Version upgrades in treatment planning Systems affect clinical application of a multi-Centre knowledge-based planning model.

Purpose: To determine if version upgrades to treatment planning system software have an impact on the clinical application of a knowledge-based planning model built in a previous version. Methods: Twenty patients' data sets treated for prostate cancer were retrospectively selected for planning on three different versions of Eclipse (Varian Medical Systems) treatment planning system, (Vn13.6, Vn15.6, Vn16.1) using a multi-centre RapidPlan model that was built in Vn13.6. Each plan was created using identical beam arrangement, and optimisation objectives and calculation settings. The RapidPlan model was also re-trained in Vn15.6 and Vn16.1 and the datasets were replanned using these models with the same method. Results: Seven plan comparisons were performed, evaluating four target metrics and eight organ at risk (OAR) metrics. Statistically significant differences to median values for target dose metrics  were observed in 10 out of 28 plan comparisons and for OARs in 23 out of 56 plan comparisons. Re‑extracted and re‑trained models in Vn15.6 and Vn16.1 improved target coverage and several OAR dose metrics. Small increases were observed in some OAR metrics for a subset of plans using the Vn15.6 model; however, the largest variations were minor (≤1.4%), including Bladder_65Gy (<1.3%), Bladder_70Gy (<0.7%), Rectum_65Gy (<0.9%), and Rectum_70Gy (<1.4%). Conclusion: Eclipse version upgrades will have varying effects on the resultant plans optimised using a RapidPlan models developed and trained in earlier versions. This study confirms the recommendation from the vendor that it is important to re-extract and re-train RapidPlan models when an Eclipse version upgrade is undertaken to ensure optimal dosimetry is achieved.