Impact of multicriteria optimization on 6MV flattening filter free volumetric modulated arc therapy for craniospinal Irradiation

Introduction: Volumetric modulated arc therapy (VMAT) is an advanced technique used for conformal dose, spare critical organs with reduced delivery time. VMAT plans were generated in Monaco™ treatment planning system (TPS) with different optimization modes. Among all, multicriteria optimization (MCO) mode is able to generate better treatment plans in many clinical sites. However, no authors have evaluated the impact of MCO on craniospinal irradiation (CSI). Therefore, purpose of this study was to evaluate the impact of MCO on CSI VMAT.Material and methods: Fifteen CSI patients treated with 23.4Gy/13 fractions followed by a boost dose using 6MV-FFF beam were chosen for this study. Dual partial arcs were used for cranium, upper spine and lower spine. Conventional VMAT (c-VMAT) plans were generated for Elekta Versa HD™ linear accelerator. Keeping all other parameters constant, c-VMAT combined MCO (MCO-VMAT) plans were generated for comparison. Conformity index (CI), homogeneity index (HI), dose coverage to PTV (D98%), organ at risk (OAR) dose, normal tissue volume (NTV) receiving dose ≥5Gy & ≥10Gy, normal tissue integral dose (NTID) , total monitor units (MU), calculation time (Ct) and delivery time (Dt) were compared. Results: CI and HI slightly improved in MCO-VMAT as compared to c-VMAT (P>0.05). No significant dose difference was observed in D98% to PTV, NTV receiving dose ≥5Gy & ≥10Gy and NTID (P>0.05). A slight increase of maximum dose to PTV was found in VMAT-MCO as compared to c-VMAT (P>0.05). Mean dose, max dose and dose volume received by OAR showed significantly less in VMAT-MCO as compared to c-VMAT (P0.05). Conclusion: For CSI, MCO-VMAT can be used without compromising target coverage, reduced OAR dose by accepting a slight increase of MUs, delivery and calculation time as compare to c-VMAT.