Plan Quality and Isotoxic Dose Escalation Investigation Using a 0.35T MR-Linac System in Ablative 5-Fraction Stereotactic Magnetic Resonance-Guided Radiation Therapy for Primary Pancreatic Cancer
R Hawranko*, K Neiderer, C Guy, E Bump, A Watson, L Yuan, T Harris, E Fields, E Weiss, W Song, Virginia Commonwealth University, Richmond, VA
Presentations
(Saturday, 3/26/2022) [Central Time (GMT-5)]
Purpose: This study investigates plan quality and isotoxic dose escalation generated by an MR-Linactreatment planning system (TPS) for 5-fraction SBRT of primary pancreatic cancer (PCa).
Methods: 20 PCa patients previously treated with a conventional Linac were retrospectively re-planned forthe 0.35T MR-Linac. For each patient, three plans were generated: the original prescriptiondose and organ at risk (OAR) constraints (Plan 1), SMART trial’s OAR constraints but with theoriginal prescription dose (Plan 2), and an isotoxic dose escalation of plan 2 where dose wasescalated until any of the SMART trial’s OAR constraints are violated (Plan 3). Conformity index,R50 conformity metrics, and standard dose-volume indices were calculated for all 60 MR-Linacplans.
Results: For Plan 1, the MR-Linac TPS successfully achieved equivalent or lower OAR doseswhile maintaining prescribed PTV coverage. Maximum dose to the small bowel was reduced onaverage by 4.97 Gy (range: 1.11-10.58 Gy). For Plan 2, the MR-Linac TPS successfully met allSMART trial OAR constraints while maintaining equivalent PTV coverage. For Plan 3, the MR-Linac TPS escalated the prescription dose from the original 25-33 Gy by an average of 36 Gy(range: 15-70 Gy). Dose to the PTV was escalated to at least 50 Gy for all plan 3’s.
Conclusion: The MR-Linac TPS can generate plans that are equivalent to conventional Linac-based plans for SBRT and has proven, in this study, to be an effective platform for safely escalating doses where suchis anticipated to translate to possible clinical benefit for PCa patients.
Funding Support, Disclosures, and Conflict of Interest: The authors acknowledge funding from the Value and Efficiency Teaching and Research grant through the VCU School of Medicine, as well as from ViewRay.
Keywords
Not Applicable / None Entered.
Taxonomy
Not Applicable / None Entered.
Contact Email