PHYSICO-DOSIMETRIC ANALYSIS OF 2D AND 3D TREATMENT PLANNING IN CLINICAL BRACHYTHERAPY: EXPERIENCE OF THE CENTER FOR NUCLEAR MEDICINE AND ONCOLOGY (SEMEY, KAZAKHSTAN)

This study presents a retrospective physico-dosimetric analysis of differences between two-dimensional (2D) and three-dimensional (3D) treatment planning approaches in high-dose-rate (HDR) brachytherapy for 20 patients with locally advanced cervical cancer. The research was conducted at the Center for Nuclear Medicine and Oncology of the Abai Region between 2023 and 2025 and included two independent cohorts of 10 treatment plans each, generated using the GammaMed Plus iX after loading system and the BrachyVision treatment planning software. A key methodological feature of the study was the use of a dedicated CT topometric provider table, enabling indexed patient positioning and eliminating geometric uncertainties during preparation for 3D treatment planning. The aim of the study was to quantitatively assess differences in clinical target volume coverage and dose exposure to organs at risk during the transition to 3D planning. To ensure methodological comparability, in accordance with GEC-ESTRO recommendations and ICRU Report 89, retrospective contouring of the high-risk clinical target volume (HR-CTV) and organs at risk (OARs) was performed on archived CT images for the 10 plans in the 2D cohort, followed by recalculation of volumetric dosimetric parameters. The primary dosimetric endpoints included HR-CTV D90 and OAR D2cc for the bladder, rectum, and sigmoid colon. Statistical analysis of independent samples demonstrated that 3D planning, supported by precise target fixation, is associated with reduced variability of HR-CTV D90, improved dose distribution conformity, and the ability to accurately assess volumetric dose exposure to organs at risk. The obtained results are consistent with international guidelines and highlight the advantages of three-dimensional planning in improving the accuracy, quality, and safety of brachytherapy in oncological practice in Kazakhstan.

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