Computed tomography-based high-dose-rate intracavitary brachytherapy for uterine cervical cancer: preliminary demonstration of correlation between dose-volume parameters and rectal mucosal changes observed by flexible sigmoidoscopy.

Purpose: To compare the dose-volume histogram (DVH) parameters obtained by three-dimensional gynecologic brachytherapy planning with the rectosigmoid mucosal changes observed by flexible sigmoidoscopy.
Methods and Materials: Between January 2004 and July 2005, 71 patients with International Federation of Gynecology and Obstetrics Stage IB-IIIB uterine cervical cancer underwent computed tomography-based high-dose-rate intracavitary brachytherapy. The total dose (external beam radiotherapy [RT] plus intracavitary brachytherapy) to the International Commission of Radiation Units and Measurements rectal point (ICRU(RP)) and DVH parameters for rectosigmoid colon were calculated using the equivalent dose in 2-Gy fractions (alpha/beta = 3 Gy). Sigmoidoscopy was performed every 6 months after RT, with the 6-scale scoring system used to determine mucosal changes.
Results: The mean values of the DVH parameters and ICRU(RP) were significantly greater in patients with a score of > or =2 than in those with a score <2 at 12 months after RT (ICRU(RP), 71 Gy(alpha/beta3) vs. 66 Gy(alpha/beta3), p = 0.02; D(0.1cc), 93 Gy(alpha/beta3) vs. 85 Gy(alpha/beta3), p = 0.04; D(1cc), 80 Gy(alpha/beta3) vs. 73 Gy(alpha/beta3), p = 0.02; D(2cc), 75 Gy(alpha/beta3) vs. 69 Gy(alpha/beta3), p = 0.02). The probability of a score of > or =2 showed a significant relationship with the DVH parameters and ICRU(RP) (ICRU(RP), p = 0.03; D(0.1cc), p = 0.05; D(1cc), p = 0.02; D(2cc), p = 0.02).
Conclusion: Our preliminary data have shown that DVH values of the rectosigmoid colon obtained by computed tomography-based three-dimensional brachytherapy planning are reliable and predictive of score > or =2 rectosigmoid mucosal changes.