A one-time screening with a fecal immunochemical test was as effective as a one-time colonoscopy for detecting colorectal cancer in an intention-to-screen analysis, but colonoscopy found more cancers among patients actually screened, investigators reported in the Feb. 23 issue of the New England Journal of Medicine.
In addition, the fecal immunochemical test (FIT) performed poorly in identifying patients with adenomas, some of which are precancerous, suggesting that reliance on this fecal test would miss opportunities to prevent cancers.
There was no difference in the stage of tumors identified by the two methods in an interim analysis of a 10-year clinical trial that will not be completed until 2021, said Dr. Enrique Quintero of the department of gastroenterology, Hospital Universitario de Canarias, Tenerife, Spain, and his associates.
In the randomized, controlled trial, the researchers had hypothesized that FIT screening every 2 years would prove to be noninferior to one-time colonoscopy "with respect to a reduction in mortality related to colorectal cancer among average-risk subjects" after 10 years. They reported these interim results after the first "round" of screening was completed in 53,302 subjects.
The study subjects were men and women aged 50-69 years who resided in eight regions of Spain and were invited to undergo screening by either FIT (26,599 subjects) or colonoscopy (26,703) at 15 tertiary care hospitals. Only 5,649 of the subjects randomly assigned to colonoscopy agreed to that screen, and only 4,953 actually underwent colonoscopy; another 1,628 opted for FIT instead. This yielded a participation rate of only 24.6% for colonoscopy.
A total of 9,353 subjects assigned to FIT agreed to that screen, and 8,983 of them actually underwent FIT; another 106 opted for colonoscopy instead. This yielded a participation rate of 34.2% for FIT.
Thus, participation rates were very low in both groups, but subjects in the FIT group were more likely to participate than those in the colonoscopy group. This may offset any apparent advantage with colonoscopy, the investigators said.
Colorectal cancer was detected in a similar number of subjects in both groups in this first round of screening. In the intention-to-screen analysis, colorectal cancer was detected in 30 subjects (0.1%) in the colonoscopy group and 33 subjects (0.1%) in the FIT group, Dr. Quintero and his colleagues said (N. Engl. J. Med. 2012;366:697-706).
In an analysis of screening that was actually performed, colorectal cancer was detected in 27 subjects (0.5%) in the colonoscopy group and 36 subjects (0.3%) in the FIT group.
Tumor stage was similar for the two groups. However, colonoscopy was superior to FIT in rate of detection of adenomas, including both advanced adenomas (odds ratio, 4.32) and nonadvanced adenomas (OR, 25.98).
Major complications developed in 24 subjects (0.5%) in the colonoscopy group, including 12 subjects who experienced bleeding and 1 who had a bowel perforation. No major complications developed in the FIT group, except among some subjects with positive findings who then underwent colonoscopy; eight of them experienced bleeding from the colonoscopy.
The primary outcome measure of the trial – the reduction in colorectal cancer mortality after 10 years – cannot be assessed yet. "The most relevant result of this interim analysis is that one-time screening with FIT was very similar to one-time colonoscopy" in detecting colorectal cancer, with no significant difference in tumor stage between the two screening methods.
Fecal Immunochemical Test Missed Adenomas
Screening with FIT yielded a similar percentage of colorectal cancers per invited person when compared with colonoscopy, but colonoscopy detected more cancers per person actually screened, wrote Dr. Michael Bretthauer and Dr. Mette Kalager.
Moreover, the diagnostic yield for adenomas in particular – lesions that may well progress to cancer – was low with FIT. This finding "indicates that FIT is not a good test for detecting adenomas," they noted.
Michael Bretthauer, M.D., Ph.D., is at Oslo University Hospital Rikshospitalet and the Cancer Registry of Norway in Oslo. Mette Kalager, M.D., is at the Harvard School of Public Health, Boston, and Telemark Hospital, Skien, Norway. Dr. Bretthauer reported ties to Falk Pharma and Olympus Optical Europe. These remarks were taken from their editorial accompanying Dr. Quintero’s report (N. Engl. J. Med. 2012;366:759-60).
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