The value of endorectal ultrasonography in the follow-up of intracavitary radiation treated early rectal cancer

In selected patients with early rectal cancer, intracavitary radiation is a successful treatment. Endorectal ultrasound has proved an accurate method for staging and selecting such cancers for treatment. The value of endorectal ultrasound in the follow-up of patients with intracavitary radiation has not been previously assessed. Between 1989 and 1991, 30 patients treated at the Hamilton Regional Cancer Centre with intracavitary radiation were assessed by endorectal ultrasound. The mean age was 65 +/- 12 years with a range of 37-78 years. There were 17 males and 13 females. All patients were treated with curative intent. The dose of radiation administered was 8963 +/- 1506 cGy over 3.5 +/- 0.7 fractions. No patient received supplemental iridium implantation. Thirty-seven endorectal ultrasounds were carried out in 30 of the intracavitary radiation treated patients. Clinical findings (digital, sigmoidoscopic, and histology) were compared with the radiologist's interpretation of the endorectal ultrasounds. Using a 2 x 2 table accepting the clinical findings as the 'Gold Standard', the sensitivity of endorectal ultrasound was 71%, the specificity 61%, the positive predictive value 53%, the negative predictive value 78% with an overall accuracy of 75%. We conclude that endorectal ultrasound in the routine follow-up of patients treated with intracavitary radiotherapy for carcinoma of the rectum is questionable.