A prospective observational study with dose volume parameters predicting rectosigmoidoscopic findings and late rectosigmoid bleeding in patients with uterine cervical cancer treated by definitive radiotherapy

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 (D(20cc), D(15cc), D(10cc), D(5cc), D(2cc), D(1cc), and D(0.1cc ,) 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, Gy(3)). 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, D(5cc), among the dose-volumetric parameters, was significant parameter for the risks of RMC ≥ score 3 and LRC ≥ grade 2 (p < 0.05). CONCLUSIONS: D(5cc) 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.