ESTRO 2021 Abstract Book

S578

ESTRO 2021

The iCycle DVHs were translated into patient-specific objective templates, with line objectives that limit dose for all volume levels for each OAR, and imported into Eclipse. Priorities and normal tissue objective settings were kept constant after tuning based on a few patients. The templates were used for automated plan optimization in Eclipse (no manual tuning), applying the same beam configurations as for the clinical plans, resulting in the iC-E plans. iC-E plans for 17 LA-NSCLC patients were compared to the CP. All patients had a 6-beam, manually planned IMRT CP in Eclipse. The prescribed dose was 60 or 66 Gy in 2 Gy fractions and dose calculation was performed with Acuros XB 15.6. The Wilcoxon signed-rank test (p<0.05) was used for statistical testing. Results Target coverage and lung dose were similar between CP and iC-E, while the average D mean for heart and esophagus was significantly reduced with iC-E [Fig. 1a, Table 1]. iC-E reduced heart D mean for 12/17 patients and esophagus D mean for 13/17 patients [Fig. 2]. For the heart, it is noticeable that while the largest reductions with iC-E are for low doses, there is also a consistent decrease in the medium-high dose range [Fig. 1b]. The maximum dose to the spinal canal, brachial plexus and patient body followed the clinic’s requirements for all plans. Table 1: Comparison of average dose metrics. Parameters in bold are significantly different. Dose metric CP iC-E PTV V 95% [%] 99.0 99.0 Lungs D mean [Gy] 13.4 13.4 Heart D mean [Gy] 8.5 7.7 Esophagus D mean [Gy] 22.9 22.3