The Dosimetric Advantages of Robust Optimization Combined With Flatten Filter Free Mode in Left Breast Cancer

Abstract Background and purposesTo explore the advantages of Robust optimization in dosimetry under flatten filter free(FFF) Mode after left breast cancer surgery.Materials and methods21 patients with left breast cancer after surgery were randomly selected from 2019 to 2020. The planned target volume (PTV) dose was prescribed 50Gy /25times and B. With or without Robust optimization were designed on the RayStation planning system with Volume rotary intensity-modulated radiotherapy technology based on the FFF Mode. By moving the center point of the field to simulated the movement of target area of the internal chest wall (0.50cm) caused by Respiratory movement, dosimetry characteristics. Using spss 23.0 to analyse the datum.Resultswhen the chest wall target moved outward, the PTV target area D98, D95, D2, CI and HI with Robust optimization were better than those without Robust, and the coverage rate of PTV-CHESTV50 was significantly higher than that without Robust optimization (P=0.000060), which was 15.39% higher than that without Robust optimization. CTVV50 coverage with Robust optimization was higher than that without Robust optimization, with an increase of 14.48%. In terms of endangering organ parameters, the average spinal cord dose of the plan with Robust optimization was 13.19% lower than that of the plan without Robust optimization, and the lung V5 of the plan without Robust optimization was slightly lower than that of the plan with Robust optimization, which was 1.80% lower than that of the plan without Robust optimization. There was no significant difference in machine execution efficiency between the two groups (P > 0.05).ConclusionsThe Robust optimization could be adopted in the development of postoperative left breast cancer radiotherapy plan, which ensures that the target dose coverage and the dose limit of organ-at-risk still meet the clinical requirements under condition of chest wall displacement caused by respiratory movement.