A novel indicator for surveillance colonoscopy following colorectal cancer resection

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Abstract
Current surveillance for recurrent intraluminal or metachronous colorectal cancer following resection is largely undertaken by colonoscopic examination of the remaining colon. The burden on colonoscopic services is high and the procedure is expensive. Immunological faecal occult blood testing (FOBT) is a sensitive and specific test for detecting colorectal cancer, and may fine tune the need for timely surveillance colonoscopy. Consecutive patients due for surveillance colonoscopy following colonic resection for cancer were prospectively studied. Each patient had a single faecal sample obtained at per rectal examination on a gloved examining finger. This was subjected to immunological FOBT in the clinic, and patients were categorized as FOBT positive or negative, according to the result. Colonoscopy as well as ultrasound or CT of the liver were performed within eight weeks of FOBT. Six hundred and eleven patients had both FOBT and colonoscopy. Fifty-nine (13.6%) were categorized as FOBT-positive. Of these, nine had biopsy-proven recurrent or metachronous cancer, 12 patients had one, or more adenomatous polyps, one patient had radiation proctitis and two patients had pan-colonic mucositis following chemotherapy. In the remaining 552 FOBT-negative patients, no cancers were found. Thirty-eight patients had polyps that were removed. The sensitivity and specificity for detecting cancer by immunological FOBT was 100% sensitivity for detecting adenomatous polyps was 24% but specificity was 93%. The immunological faecal occult blood test provides sensitive detection of metachronous and recurrent cancer in postoperative surveillance. Routine application may be used to reduce the frequency of colonoscopic surveillance, as a negative FOBT may be taken as a sign that colonoscopy may be deferred safely.