Comparisons between the KKU-model and conventional rectal tubes as markers for checking rectal doses during intracavitary brachytherapy of cervical cancer.

Abstract

To compare the KKU-model rectal tube (KKU-tube) and the conventional rectal tube (CRT) for checking rectal doses during high-dose-rate intracavitary brachytherapy (HDR-ICBT) of cervical cancer. Between February 2010 and January 2011, thirty -two patients with cervical cancer were enrolled and treated with external beam radiotherapy (EBRT) and intracavitary brachytherapy (ICBT). The KKU-tube and CRT were applied intrarectally in the same patients at alternate sessions as references for calculation of rectal doses during ICBT. The gold standard references of rectum anatomical markers which are most proximal to radiation sources were anterior rectal walls (ARW) adjacent to the uterine cervix demonstrated by barium sulfate suspension enema. The calculated rectal doses derived from actual anterior rectal walls, CRT and the anterior surfaces of the KKU-tubes were compared by using the paired t-test. The pain caused by insertion of each type of rectal tube was assessed by the visual analogue scale (VAS). The mean dose of CRT was lower than the mean dose of ARW (Dmean0-Dmean1) by 80.55±47.33 cGy (p-value<0.05). The mean dose of the KKU-tube was lower than the mean dose of ARW (Dmean0-Dmean2) by 30.82±24.20 cGy (p-value<0.05). The mean dose difference [(Dmean0-Dmean1)-(Dmean0-Dmean2)] was 49.72±51.60 cGy, which was statistically significant between 42.32 cGy -57.13 cGy with the t-value of 13.24 (p-value<0.05). The maximum rectal dose by using CRT was higher than the KKU-tube as much as 75.26 cGy and statistically significant with the t-score of 7.55 (p-value<0.05). The mean doses at the anterior rectal wall while using the CRTs and the KKU-tubes were not significantly different (p-value=0.09). The mean pain score during insertion of the CRT was significantly higher than the KKU-tube by a t-score of 6.15 (p-value<0.05) CONCLUSIONS: The KKU-model rectal tube was found to be an easily producible, applicable and reliable instrument as a reference for evaluating the rectal dose during ICBT of cervical cancer without negative effects on the patients.