SAN DIEGOBased 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 plans flexible sigmoidoscopy colorectal cancer screening
program, depending on patient preference, the practice setting, and
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
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
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.