Rapidplan As a Surrogate for Clinically Achievable OAR Sparing In Pancreatic SBRT Planning with Monaco
Abstract
Purpose
Treatment planning for pancreatic SBRT remains challenging due to proximity and overlap of the target with the critical organs-at-risk (OARs). This study uses RapidPlan-predicted dose volume histograms (DVHs) to guide treatment planning in Monaco.
Methods
A RapidPlan model previously developed at our institution in the Eclipse planning system was applied to 11 randomly selected pancreatic SBRT patients followed by comparison with clinical plans. The dose constraints were used as a reference to generate a template in Monaco with the physician-guided automation (PGA) script using quadratic overdose, overdose DVH, target penalty and maximum dose cost functions. Plans utilized a 14 field IMRT approach on the Versa machine avoiding RF coils mimicking approach used for the MR Linac completing two stage optimization applying the planning template as a starting point. Dosimetric comparisons were performed across the plans using the Wilcoxon signed-rank test at p>0.05 for significance testing.
Results
No significant differences were seen in target coverage, plan heterogeneity or OAR doses between RapidPlan versus the clinical plan. Moreover, both concurred in 17 out of 19 dosimetric variables in their ability to meet the goal/acceptable criteria with the exception of duodenum V15Gy where RapidPlan exceeded the limit by 0.19 cc, hence missing the goal but meeting the acceptable criteria and stomach V20Gy where RapidPlan was able to meet the goal. Monaco plans agreed with RapidPlan in 18 of the 19 dosimetric variables with the exception of stomach V20Gy with regards to meeting goal versus acceptable criteria. Monaco plans met constraints within 1-3 optimizations with manual adjustments to cost functions as necessary.
Conclusion
Although preliminary, these results show promise in potentially using RapidPlan as surrogate for clinically achievable OAR sparing for the given anatomy while planning a case in Monaco. Future work will entail transporting these templates to planning with the MR Linac.