ESTRO 2023 - Abstract Book

S1924

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ESTRO 2023

80.1% for each risk group (p=0.017). Five-year OS was 100%, 100%, and 93.8% for each risk group, which was statistically insignificant (p=0.814). There was no incidence of grad e ≥ 3 acute or late gastrointestinal and gastrourinary toxicity.

Conclusion The significant prognostic factors for DFS of early-stage endometrial cancer were grade, largest mass, and depth of invasion in patients treated with postoperative vaginal brachytherapy. Based on the abundance of these prognostic factors, we suggested risk group criteria consisting of low, intermediate, and high risk group. According to the survival analysis, high- risk group showed significantly low DFS, compared with low and intermediate risk groups. Postoperative chemotherapy or external beam radiotherapy might be recommended for the high risk group patients. Further studies including molecular profiles of endometrial cancer are needed to discover possible novel risk factors. Prospective randomized trial is warranted to determine whether this suggested risk group criteria could be a tool for tailoring adjuvant treatment for early-stage endometrial cancer.

PO-2139 Improvements of Elekta Fletcher type applicator in brachytherapy using 3D printing technology

A. T š i ž ik 1 , N. Saveljev 1 , M. Tigasson 2

1 The North Estonia Medical Centre, Radiotherapy, Tallinn, Estonia; 2 The North Estonia Medical Centre, Medical Technology Division, Tallinn, Estonia Purpose or Objective The aim of this research is to improve clinical target volume coverage for the Fletcher type applicator from Elekta by making 3D printing add-on. Materials and Methods The 15 mm ovoid library model was exported from the Oncentra 4.6.0 planning system as an xml file. Blender 2.93.0 design software was used to modify a virtual 3D model. The ovoids were joined together in the coronal plane with the halves of the straight sides, leaving a tandem opening in the center for further fixation of the resulting monoovoid. This solution provides an opportunity to install additional needles in the direction of the bladder and rectum, which is not possible with the geometry of the standard applicator. The resulting model was imported back into the Oncentra planning system (1) to create a pretreatment plan, i.e. determine new interstitial needle locations, transfer them to a three- dimensional model, and draw them in Blender software. Biomed Clear Resin (Formlabs) was used in the production of monoovoid. Parts printed with BioMed Clear Resin are compatible with common sterilization methods. To verify the geometric properties of the monoovoid, the finished monovoid (2) was assembled with other parts of the applicator and scanned with CT using CT markers on the needles. According to the CT markers in the Oncentra system, the locations of the needles were reconstructed and the same reference points used in the modeling stage were built.

VeriSoft 8.0 software was used to compare the dose distributions of the original and 3D printed applicators.