Purpose: We assessed the value of dose-volumetric parameters predicting rectosigmoid mucosal changes (RMC) and late rectosigmoid complications (LRC).
Methods: Between January 2004 and February 2006, 77 patients with stage IB-IIIB cervical cancer underwent external beam radiotherapy and computed tomography (CT)-based intracavitary irradiation. Total dose to the rectal point and several dose-volumetric parameters for rectosigmoid colon (D20cc, D15cc, D10cc, D5cc, D2cc, D1cc, and D0.1cc , defined as the minimal doses received by the highest irradiated volumes of 20, 15, 10, 5, 2, 1, and 0.1 cc, respectively), were calculated using the equivalent dose in 2 Gy fractions (α/β = 3, Gy3). The RMC and LRC were graded by rectosigmoidoscopy and Radiation Therapy Oncology Group criteria every 6 months, respectively.
Results: Of 77 patients, 27 (35.1%) patients developed RMC ≥ score 3 and 22 (28.6 %) patients developed LRC ≥ grade 2. There was a positive correlation between RMC score and LRC grade (r = 0.728, p < 0.001). In multivariate analyses, D5cc, among the dose-volumetric parameters, was significant parameter for the risks of RMC ≥ score 3 and LRC ≥ grade 2 (p < 0.05).
Conclusions: D5cc may be a more reliable estimate than other dose-volumetric parameters for predicting the risk of RMC ≥ score 3 and LRC ≥ grade 2 in CT-based brachytherapy.