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

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 (D 100 , D 90 , D 50 , 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.

Equivalent dose in 2 Gy (EQD2) to pelvic lymph nodes using volume based prescription for three brachytherapy applicators — a dosimetric retrospective analysis

“…Matsukawa et al correlated dose to point B with dose to the pelvic lymph nodes using two applicators used in ICBT. They found that the dose delivered to point B and the PLN groups were not significantly different between TO and tandem and cylinder [12]. Similarly, we observed there was no difference in the median EQD2 to the pelvic lymph nodes across the three applicators.…”

“…Similar studies have been done by Chua et al [8], Lee et al [11], Lee Y et al [12] and Matsukawa et al [13], where they did CT based planning but prescribed to point A.…”

An exploratory study of the dose correlation between point B and metastatic lymph nodes in three‐dimensional high‐dose‐rate brachytherapy for cervical cancer

“…This finding identifies another method of delineating the lymph nodes in brachytherapy for cervical cancer, that is, delineating the overall lymph node area. Matsukawa et al 16 . reported that among 49 patients with cervical cancer treated with brachytherapy, the obturator lymph node group dose was 53% of the point B dose, the internal iliac lymph node group was 22% of the point B dose, and there was a strong dose correlation between the D 50 in obturator lymph node group and point B.…”