ESTRO 2023 - Abstract Book

S1928

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ESTRO 2023

Conclusion Inter-fraction OAR motion occurs in cervical brachytherapy and can necessitate prescription dose reduction. The superior and middle subsections of the rectum and bladder experienced the greatest percentage deviations on the pre-fraction 2 and 3 CTs compared to the pre-fraction 1 CT. Dosimeters should be placed in a range of locations within the rectum and bladder at the level of the HRCTV.

PO-2143 Comparison of doses according to bladder classification in brachytherapy for cervical cancer

E. Choi 1 , Y. Oh 1 , M. Kim 2

1 Keimyung University Dongsan Hospital, Keimyung University School of Medicine, Department of Radiation Oncology, Daegu, Korea Republic of; 2 Keimyung University Dongsan Hospital, Department of Radiation Oncology, Daegu, Korea Republic of Purpose or Objective The typical local treatments used for cervical cancer are surgery and radiation therapy. Radiation therapy includes external radiation therapy and intracavitary brachytherapy using isotopes (192Ir), and may be used in parallel, sequentially, or alone as needed. For tumors larger than 4 cm or stage Ⅱ or higher, radiation therapy and chemotherapy are mainly combined, and brachytherapy is essential after external irradiation. This study aimed to investigate the impact of classification technique of type of bladder filling (ToBF) to optimum the bladder volume (BV), dose saving effects of organs and risk (OARs) and tumor for cervical cancer brachytherapy. Materials and Methods This retrospective study was conducted on 269 patients who received intracavitary brachytherapy for cervical cancer between 2016 and 2022. Treatment doses to D90 of HR-CTV, D2cc of bladder, D2cc of rectum, D2cc of bowel and D2cc of sigmoid were calculated by using forward planning technique based on CT and MR images. The ToBF classification with an inserted applicator was divided into three types (tilted: type T, curved: type C and round: type R). The ToBF was classified into three subgroups according to the BV (cm3) as a group A: BV<200 cc, a group B: 200 cc

Figure 1. Representative 3D image and CT image examples according to the bladder type classification : a,b,c=R type, d,e,f=C type, g,h,i=T type (Black arrow and red area=bladder).

Results