The prediction of late rectal complications following the treatment of uterine cervical cancer by high-dose-rate brachytherapy

PURPOSE: This study aimed to correlate patient, treatment, and dosimetric factors with the risk of late rectal sequelae in patients with uterine cervical cancer treated with external beam radiation therapy (EBRT) and high dose rate intracavitary brachytherapy (HDRICB). METHODS AND MATERIALS: From September 1992 to December 1995, a total of 128 patients with uterine cervical cancer, who were treated and survived more than 12 months, were evaluated. After EBRT with 40-44 Gy/20-22 Fr/4-5 weeks to the whole pelvis, the dose was boosted up to 54-58 Gy with central shielding for patients with bilateral parametria of Stage IIb or greater. HDRICB consisted of three to four insertions at doses of 5-7.2 Gy (to Point A) at intervals of 1 week. Patient and treatment factors were analyzed using logistic regression analysis and the cumulative rectal biologic equivalent dose (CRBED) was calculated. RESULTS: After 30-75 months of follow-up (median, 43 months), 38 patients (29.7%) had late rectal sequelae. Patients who had Stage IIb-IVa disease, cumulative rectal dose (external RT + total ICRU rectal dose) greeater than 65 Gy, or age greater than 70 years had a high risk of developing late rectal sequelae. When 110 Gy was used as the cut-off value, 19.6% (10 of 51) of patients whose CRBED was less than 110 Gy had rectal complications, while 36.4% (28/77) of patients whose CRBED was greater than 110 Gy developed rectal complications. CONCLUSION: Risk factors of late rectal complications were advanced stage, age greater than 70 years, and cumulative rectal dose of greater than 65 Gy.