Assessment of the anatomical position of point B and the relationship between point B dose and the dose delivered to pelvic lymph nodes in CT-based high-dose-rate brachytherapy for uterine cervical cancer

Hideaki Matsukawa; Tomonari Sasaki; Ryota Hirayama; Taka-Aki Hirose; Jun-Ichi Fukunaga

doi:10.5114/jcb.2019.84419

Assessment of the anatomical position of point B and the relationship between point B dose and the dose delivered to pelvic lymph nodes in CT-based high-dose-rate brachytherapy for uterine cervical cancer

J Contemp Brachytherapy. 2019 Apr;11(2):137-145. doi: 10.5114/jcb.2019.84419. Epub 2019 Apr 29.

Authors

Hideaki Matsukawa¹, Tomonari Sasaki², Ryota Hirayama³, Taka-Aki Hirose³, Jun-Ichi Fukunaga³

Affiliations

¹ Division of Medical Quantum Sciences, Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Japan.
² Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Japan.
³ Division of Radiology, Department of Medical Technology, Kyushu University Hospital, Japan.

Abstract

Purpose: To examine the anatomical position of point B and the relationship between the dose at point B and the dose delivered to the pelvic lymph nodes in computed tomography (CT)-based brachytherapy for cervical cancer.

Material and methods: Forty-nine cervical cancer patients were treated at Kyushu University Hospital. For all cases, planning CT images obtained after the applicator insertion were imported to an Oncentra Brachy (Elekta AB, Stockholm, Sweden), and points A (dose prescription, 6 Gy) and points B were set according to the Manchester method. The pelvic lymph node regions (external iliac, internal iliac, and obturator) were contoured, and the anatomic positions of 98 points B in 49 patients were examined. Dose volume histogram (DVH) parameters (D₁₀₀, D₉₀, D₅₀, D_2cc, D_1cc, and D_0.1cc) were calculated for each lymph node region and compared with the point B dose.

Results: The mean bilateral dose to point B was 1.70 ±0.18 Gy, and 26 (27%) of 98 points B were not located in any pelvic lymph node regions. The DVH analysis indicated a low degree of correlation overall, and all values were significantly different from point B doses (p < 0.05), except for D_0.1cc of the external iliac node (p = 0.0594) and D_1cc of the internal iliac node (p = 0.0711).

Conclusions: We investigated the anatomical location of point B in patients with cervical cancer who underwent brachytherapy, and the DVH analysis revealed that the point B dose was a poor surrogate for the dose delivered to the pelvic lymph nodes.

Keywords: CT; brachytherapy; cervical cancer; lymph nodes; pelvis.