Dados do Trabalho

Título

Comparative dosimetric study between two-dimensional and three-dimensional planning of high-dose rate intracavitary brachytherapy for cervical cancer

Introdução

The treatment of choice for patients with locally advanced cervical cancer is the combination of radiotherapy and chemotherapy, and the radiotherapy modality used is the combination of external radiotherapy and brachytherapy. In order to deliver high doses in target volumes and reduce the dose in healthy tissues, the three-dimensional brachytherapy technique emerges.

Objetivo

This paper aims to carry out a comparative dosimetric study between two-dimensional and three-dimensional planning of high-dose rate (HDR) brachytherapy in patients with locally advanced cervical cancer.

Método

The radiotherapy plans of 5 patients submitted to teletherapy with a dose of 50Gy in 25 fractions and concomitant BOOST in positive lymph nodes followed by high dose rate brachytherapy were selected. The sum of the doses of teletherapy and brachytherapy was performed by calculating the biologically equivalent dose in 2Gy per fraction (EQD2) using the linear-quadratic model with 10Gy alpha/beta for tumor effects and 3Gy alpha/beta for late damage to normal tissue . The percentage differences between the dose obtained in the planning and the recommended dose for the target volume (high-risk CTV) and risk organs (rectum and bladder) were calculated, followed by a comparison between the differences found for the two-dimensional and three-dimensional planning.

Resultados

For the assessment of dose coverage, the EQD2 dose of 75Gy was considered, comparing the volume coverage of 98% of the high-risk CTV in relation to point A, differences ranging from 1.46% to 17.65 were shown %. Regarding the restriction dose limit for the rectum point and the volume of 2cm3 of the rectum, differences between 0.85% and 11.42% were evidenced. The bladder structure to be evaluated showed a difference ranging from 1.38% to 30.48% between the punctual dose and the volume of 2cm3 bladder.

Conclusão

Thus, it is concluded that considering the evaluated plans, there was no statistical correlation between the dosimetric measures for assessing the structures of organs at risk (bladder and rectum) or for assessing dose coverage (high-risk CTV) when compared two-dimensional and three-dimensional brachytherapy planning evaluation parameters.

Palavras-chave

Brachytherapy, three-dimensional, cervical cancer