LATE RECTAL COMPLICATIONS IN PATIENTS WITH CARCINOMA OF THE CERVIX TREATED WITH RADIOTHERAPY ALONE

Abstract

Purpose: To evaluate the frequency and severity of late rectal complications in cervical cancer patients treated with radiotherapy alone, combination of external beam irradiation and high dose rate intracavitary radiation, at Section of Radiation Oncology, Faculty of Medicine, Chiang Mai University and to assess the correlation between the biological effective dose (BED) to the rectum and the development of late rectal complications.  

Materials and Methods: Between January 1995 and June 1997, 76 patients with cervical cancer stage IB to IIIB treated with radiotherapy alone were included. Radiotherapy consisted of 40-60 Gy external beam radiation plus 4-6 high dose rate intracavitary to a total dose of approximately 30 Gy to point A, defined as 2 cm. above the external os and 2 cm. lateral to the axis of the intrauterine tube. Patient characteristics, radiation parameters and symptoms of late rectal complications were collected from the medical records. Severity of late rectal complications were clinically graded according to RTOG late morbididity grading scheme and endoscopically graded according to Gilinsky classification. Correlation between clinical and endoscopic grading, biological effective dose and late rectal complications were assessed.  

Results: With a median follow up time of 13 months, the overall rate of late rectal complications (RTOG grade 1-4) was 34% (26 (26 of 76 patients). The median time for development of complications was 9 months after completion of treatment. Twelve percent of patients had high grade late rectal complications (RTOG grade 3, 4). All patients who were selected for sigmoidoscopy had histologically proven for radiation proctitis. Clinical RTOG grading significantly correlated with endoscopically grading. The correlation between the biological effective dose delivered to the rectal reference point and the development of late rectal complications shows a strong dose-response with a threshold for complications occurring at approximately 100 Gy3 and a complication probability of 30%.  

Conclusion: This investigation revealed a significant correlation between the biological effective dose and the development of late rectal complications in patients with carcinoma of the cervix undergoing radiotherapy alone. Using the linear-quadratic model applied for our clinical results, we have established a threshold for the incidence of late rectal complication. The threshold is consistent with other studies.