Purpose: This study evaluated the dose delivered to lymph nodes (LNs) by brachytherapy (BT) and the effect of BT image-guided optimization on the LN dose.
Methods and materials: Twenty-five patients with locally advanced cervical cancer were retrospectively analyzed, 16 patients of them had LN involvement. The patients received whole pelvis intensity-modulated radiation therapy (45-50 Gy/25-30 fx) to whole pelvis and two fractions of MRI pulsed-dose-rate BT. The delineated LN groups were para-aortic, inguinal, common iliac (CI), external iliac, internal iliac, obturator, and presacral. For each LN group, D98%, D50%, and D2% (the dose that covers 98%, 50%, and 2% of the volume, respectively) were evaluated for optimized and standard BT plans. The correlation between total reference air kerma (TRAK) and D50% of the LN groups was evaluated.
Results: BT contributed considerable dose (mean D50% was 3.8-6.2 Gy equivalent total dose in 2-Gy fractions) to the pelvic LN (external iliac, internal iliac, obturator, and presacral) in optimized plans, whereas less-dose contribution to CI, para-aortic, and inguinal (mean D50% was 0.5-1.9 Gy equivalent total dose in 2-Gy fractions) was observed. Optimized plans delivered less dose to the LNs as compared with standard plans, although differences only amounted to a mean of 0.2-0.9 Gy (D50%). TRAK showed a significant correlation with LN D50% for all LN groups except CI, although only 19-38% of the dose variation could be explained by the TRAK.
Conclusions: BT contributes considerable dose to pelvic LNs and should be considered in the evaluation of total LN doses.
Keywords: Brachytherapy; Cervical cancer; Inguinal lymph node; MRI guided; Para-aortic lymph node; Pelvic lymph node; Radiation dose.
Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.