Dose to pelvic lymph nodes in image based high dose rate brachytherapy of carcinoma cervix

Abstract

The aim of this study is to analyse the dosimetry to the pelvic lymph nodes and its correlation to point B using CT based high dose rate brachytherapy of carcinoma cervix.Background: Conventionally, dose to pelvic lymph nodes from intracavitary brachytherapy was reported by point B and by the reference points of the lymphatic trapezoid. Materials and methods: 30 consecutive CT based high dose rate applications were reviewed between February and March 2016. The high risk clinical target volume and the organs at risk and the pelvic nodal groups were contoured. DVH parameters for the right and left obturator nodal group, right and left external iliac nodal group and right and left internal iliac nodal group were recorded. Right and left point B doses were also recorded.Results: On analysis of the combined dose, it was found that all the DVH parameters were significantly different from point B, except the D100 obturator and D2cc internal iliac lymph node. There was a significant correlation between all DVH parameters and point B, except D2cc, D1cc and D0.1cc of external iliac. The obturator group received the highest dose contribution from brachytherapy. The mean D90 dose received per fraction for the obturator, external iliac and internal iliac nodes was 2.7 Gy, 1.17 Gy and 1.41 Gy, respectively.Conclusions: There is a significant dose contribution to the pelvic lymph nodal groups during intracavitary brachytherapy. There is a low degree of correlation between point B dose and dosimetric parameters of the individual nodal groups. Hence, it is important to analyse the dose delivered to individual nodal groups during intracavitary brachytherapy, at least in patients with enlarged lymph nodes to calculate the cumulative dose delivered.

Evaluation of doses to pelvic lymph node regions from image-guided high-dose-rate interstitial brachytherapy for carcinoma of the uterine cervix

“…While D 90 to OB-N from ICRT reported by Rangarajan et al . [ 27 ] was comparable to our study (38.5 ±10% vs. 38.59 ±4.74% respectively), D 2cc to OB-N was lower compared to our study (58.5 ±18% vs. 121.48 ±4.94% respectively). Owing to proximity of the OB-N to the interstitial needles, this group receives a very high dose from the ISBT and hence it would be prudent to take this into consideration while planning to boost positive lymph nodes in the OB-N region.…”

“…[ 12 ] and Rangarajan et al . [ 27 ], as illustrated in Table 4 ; the doses to II-N D 2cc were higher as compared to both these studies. The region of II-N in proximity to the needles will have a higher dose (D 2cc ) than the average dose received by the entire II-N group (D 90 ), and hence the location of the positive II-N is important to predict the incidental doses to that region, and this must be individualized on a patient-to-patient basis.…”

“…Historically, doses received by the PLN during ICRT were estimated by the lymphatic trapezoid of Fletcher, which represented the dose to the lower para-aortic, lower common iliac and middle external iliac lymph nodes, and by the pelvic wall points, which denote the dose to the obturator lymph nodes [ 13 ]. Few studies have evaluated the dosimetry of the different pelvic lymph nodal groups with ICRT applications [ 14 , 15 , 27 ]. It has been concluded that there is a significant dose supplement to the PLN during ICRT.…”

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

“…The dose contribution of brachytherapy to the pelvic lymph node group of patients with cervical cancer is clear, but the correlation between doses to point B and doses to any other lymph node group is modest. 19 This perspective is similar to that of the current study. Data In cervical cancer patients with lymph node metastases, 3D HDR brachytherapy contributes significantly to the pelvic lymph node dose, but less to the para-aortic and inguinal lymph node doses.…”

“…identified the dose of the para‐aortic, common iliac, external iliac, internal iliac, presacral, and obturator lymph node groups, and found that brachytherapy significantly contributed to the dose of the pelvic lymph nodes. The dose contribution of brachytherapy to the pelvic lymph node group of patients with cervical cancer is clear, but the correlation between doses to point B and doses to any other lymph node group is modest 19 . This perspective is similar to that of the current study.…”