Reasonable to Add Immunochemical FOBT to Sigmoidoscopy Screening

SAN DIEGO—Based on preliminary test results, researchers at Kaiser Permanente Northern California and the University of California, San Francisco, believe that immunochemical fecal occult blood testing (IFOBT) would be a reasonable addition to a managed care plan’s flexible sigmoidoscopy colorectal cancer screening program, depending on patient preference, the practice setting, and cost constraints.

James E. Allison, MD, San Francisco General Hospital, reported the findings at an American Gastroenterological Association research forum held during the Digestive Disease Week conference.

He said that the study was conducted in an attempt to prospectively determine the added yield of advanced neoplasms IFOBT would bring to an established colorectal cancer screening program utilizing sigmoidoscopy alone.

Dr. Allison said that the study was conducted at three Kaiser Permanente facilities in Northern California. “Average-risk patients who were referred for a screening sigmoidoscopy were offered screening with two IFOBTs,” Dr. Allison said. “These were FlexSure OBT and HemeSelect. Those testing positive on either test were offered colonoscopy. Those testing negative were referred for sigmoidoscopy.”

More Than 6,000 Screened

Dr. Allison said that IFOBT cards were received from 6,079 patients, and interpretable test results were obtained from 5,944. Of those patients, 200 had a positive test. A colonoscopic examination was completed in 186 of the patients with a positive IFOBT (mean age, 61).

Advanced colonic neoplasia was found in 63 participants (positive predictive value, 34%). Advanced proximal neoplasia was found in 25 subjects, and proximal cancer in three (positive predictive value, 6.5%). The number of patients needed to screen to detect a single advanced neoplasm was 120; for advanced proximal neoplasia, 301, and for proximal cancer, 2,514.

Of the advanced proximal neoplasms, 12 lacked a distal marker lesion and therefore would not have been found with sigmoidoscopy screening alone. Two of the three proximal cancers also lacked a distal marker.

For these groups, the number of patients needed to screen to detect additional lesions was 628 for advanced proximal neoplasm and 3,771 for proximal cancer.

Reason to Add Test

“We determined that immunochemical fecal occult blood tests do uncover a proportion of advanced proximal neoplasms that would not be detected by sigmoidoscopy alone,” Dr. Allison said. “That may be a reason to add the test to sigmoidoscopy in colorectal screening programs, even though a substantial number of people will need to be screened to detect cancers not detectable by sigmoidoscopy.”

Dr. Allison acknowledged that the researchers were not sure as to the reasons behind the low yield of advanced colonic neoplasia beyond the reach of the sigmoidoscope in this study.

It may be that the IFOBT was more sensitive to distal lesions, he said, or it may relate to the age of the patient population.

“The mean age of the population was 61, and therefore, we were screening a younger population,” he stated. “In an older population, we might have found more lesions beyond the reach of the sigmoidoscope.”

The researchers’ next step is to look at the find rate of sigmoidoscopy, the miss rate of IFOBT, and the miss rate of sigmoidoscopy, Dr. Allison said.