Dosimetric comparison between two brachytherapy applicators in cervical cancer treatment

Abstract

Objective To compare the dosimetric parameters between the use of Tandem and Ring (TR; Nucletron#090.617) or Tandem and Ovoid (TO; Nucletron#189.730) applicators during three-dimensional (3D) high-dose rate (HDR) brachytherapy (BT) for cervical cancer. Methods The records of 40 cervical cancer (ⅡB-ⅣA) patients treated with 3D-image-guided HDR-BT were reviewed. Of these 40 patients, 20 were treated with the TO applicator, and 20 with the TR applicator. The D100% and V150% of the clinical target volume (CTV) and the D2 cc of organs at risk (OAR)(the rectum, bladder, and small intestine) during 3D-HDR-BT using TO and TR were compared using the independent sample t-test. Results Overall metrics: CTV volume: 66.04±13.86 cm3(TR) vs. 65.67±15.08 cm3(TO)(P=0.052); CTV D100: 3.71±0.34 Gy (TR) vs. 3.37±0.49 Gy (TO)(P=0.016); CTV V150%: 0.54±0.02(TR) vs. 0.56±0.04(TO)(P=0.034); rectum D2 cc: 3.38±0.30 Gy (TR) vs. 2.95±0.80 Gy (TO)(P=0.037); bladder D2 cc: 4.33±0.39 Gy (TR) vs. 2.93±1.27 Gy (TO)(P=0.00); and small intestine D2 cc: 3.04±1.02 Gy (TR) vs. 3.41±0.57 Gy (TO)(P=0.171). Conclusions TR has better CTV coverage than TO during 3D HDR brachytherapy for cervical cancer. In addition, D2 cc of the rectum and bladder were both higher with TR than with TO, though there is no significant dosimetric difference in the small intestine between the two applicators. Therefore, tumor location, extent of invasion, and vaginal conditions should be considered when selecting the suitable applicator for the treatment of cervical cancer. Key words: Applicators; Cervical neoplasms/brachytherapy; Dosimetry