A prospective study to assess the bladder distension effects on dosimetry in intracavitary brachytherapy of cervical cancer via computed tomography-assisted techniques

Abstract

Background and purpose Intracavitary brachytherapy (ICBT) is as important as external beam radiotherapy (EBRT) for the radical radiotherapy of uterine cervical cancer. The degree of urinary bladder distension during ICBT may affect the dose distribution in the bladder and rectum, to which an overdose may increase the chance of developing treatment-related complications. The purpose of this prospective study was to assess and quantify the impact of bladder distension on dosimetry in ICBT in patients with cervical cancer. Patients and methods We recruited 20 patients with cervical cancer during a 12-month period. Inclusion criteria included pathological diagnosis of cervical cancer with IA to IIIB stages, and intact uterus. Patients were evaluated for brachytherapy after EBRT, and eligible individuals (cervical os could be identified clearly) were invited enter to this protocol to receive ICBT. In the first brachytherapy, bladder preparation (evacuation and distension by a Foley catheter) and CT scan were performed soon after the insertion of CT-compatible applicators. Then the bladder wall doses [median dose, maximum dose and dose–volume histograms (DVH)] were calculated via the PLATO computer planning system ( Nucletron PLATO-RTS version 2.0). The individual data regarding doses and DVH were collected and compared. Bladder distension may shift the applicator position, and posterior displacement of the applicator system may increase the dose to the rectal wall, so this effect was also evaluated. Results All the continuous variables of these 20 patients followed a normal distribution. By paired t-test and multiple linear regression analysis, we found that bladder distension statistically significantly decreased the median bladder wall dose with an average reduction of 48% of the dose of an empty bladder ( P<0.001), and the maximum dose did not change; on the other hand, the bladder distension did not have any adverse effects on the rectal wall doses. Conclusions Using CT-assisted three-dimensional techniques to assess the bladder and rectal wall doses is feasible. Bladder distension reduces the median dose in the bladder wall, which may reduce treatment-related complications.