Dosimetric comparison of two-dimensional versus three-dimensional intracavitary brachytherapy in locally advanced cervical cancer

Abstract

Introduction The aim of this study was dosimetric comparison of two-dimensional (2D) with three-dimensional (3D) planning for high-dose-rate intracavitary brachytherapy (HDR-BT) in locally advanced cervical cancer by dose evaluation in given International Commission on Radiation Units and Measurements (ICRU) reference points, as well as in target volume and organs at risk.

Methods Sixty-six sessions of HDR-BT were performed in 22 patients, with 3D planning, but a virtual 2D plan for dosimetric comparison was also made. 2D planning was performed on radiography obtained by C-arm in ICRU points, and 3D planning in volumes delineated on computer tomography.

Results The comparative analysis indicated a significant mean dose difference of point A left (p = 0.00014) and right (p = 0.003), through higher doses in 2D and lower doses in 3D reconstructed points A. According to the dose volume histograms, 56.88% and 61.41% mean target volume received 100% and 90% of the prescribed dose, respectively. 2D bladder analysis showed a mean dose of 3.487 Gy in ICRU points, while in 3D analysis a maximum mean dose of 8.804 Gy and a mean dose of 4.716 Gy in 2 cm³ volume. 2D analysis showed a rectal mean dose of 2.892 Gy in ICRU points, while 3D analysis showed maximum mean dose of 6.411 Gy and 3.947 Gy mean dose in 2 cm³ volume.

Conclusion 2D planning showed unreal higher doses in the ICRU points for the target and lower doses for the organs at risk.

Keywords: cervical cancer; intracavitary brachytherapy; organs at risk; target volume