EP-1625: A dosimetric analysis of semi-automated knowledge-based VMAT planning for rectal cancer patients

Material and Methods: Created by experts following consistent contouring and planning protocols, clinically approved SIB VMAT plans for 150 patients were selected, 80 which were added to the library of Varian RapidPlan to train the DVH estimation model. The other 70 plans were duplicated whose MLC sequences were re-optimized using the model-generated DVH objectives. All plans were normalized to PTV95% ≥ 41.8 Gy and PGTV95% ≥ 50.6 Gy before comparing: dose coverage of GTV and CTV; homogeneity index (HI), conformal index (CI), hotspot volume receiving over 107% of prescription (V107%_PGTV), mean dose and dose to 50% volume of femoral head (Dmean_FH and D50%_FH) and urinary bladder (Dmean_UB and D50%_UB) respectively. Average DVHs of 70 patients were plotted. The normally and non-normally distributed data sets were analyzed using paired samples t-test and Wilcoxon signed ranks test respectively, setting P<0.05 as significant.