Dose to pelvic lymph nodes in locally advanced cervical cancer during high-dose-rate brachytherapy with tandem-ring applicators

Purpose: The present study aimed to assess the correlation between dose to pelvic lymph nodes and to point B with tandem-ring (TR) applicators for intra-cavitary brachytherapy treatment of locally advanced cervical cancer. Material and methods: Cervical cancer patients treated at brachytherapy department of Lucien Neuwirth Cancer Center, from 2015 to 2018, were included. Target delineation was performed in compliance with GEC-ESTRO guidelines. Revised American Brachytherapy Society (ABS) point A was determined (A(RN) (right) and A(LN) (left)) as well as Manchester point B. Prescription dose was 25-35 Gy in 5 fractions. Pelvic lymph nodes were delineated, then dose to points A and B, and dose-volume histogram (DVH) parameters of delineated lymph nodes were extracted. Significant relationships or correlations between lymph nodes reference points, dosage to points B, and their DVH parameters were investigated. Results: The mean dose and mean percentage of the prescription dose to the left and right points B were 4.6 +/- 0.18 Gy and 82.08 +/- 0.72%, respectively. Pearson correlation coefficient R = 0.81 (p-value = 0.00) between dose to A(RN) and A(LN) points and prescription dose was obtained. Negative correlation between CTVHR volume and difference between French and ABS prescription points was found. Conclusions: Dose to point B can be a moderate surrogate for maximum, minimum, and median dose to the internal iliac and presacral lymph node, but cannot be for maximum dose to the obturator lymph node. Points B cannot be a reliable substitute for common and external iliac chains.