Blood Test Shows Promise in Detecting Colorectal Cancer and Adenomas

ORLANDO, FL—Approximately 1 million new cases of colorectal cancer cases are diagnosed annually worldwide. In the majority of cases, the diagnosis is made at a late stage, resulting in a poor prognosis. Currently, the primary screening methods for colorectal cancer and colorectal adenomas are c

olonoscopy and fecal occult blood testing; however, colonoscopy remains underutilized because of its invasive nature, and stool testing lacks sensitivity. To help improve early detection, when the chance for survival is greatest, researchers from Tel Aviv Sourasky Medical Center in Israel sought to develop a reliable blood test for detecting colorectal adenomas and colorectal cancers.

The researchers’ earlier study had demonstrated a correlation between CD24 expression and colorectal cancer; CD24 is thought to be produced early in the development of colorectal cancer and to contribute to the spread of tumor cells. To assess if CD24 could be a potential biomarker, the researchers evaluated CD24 protein expression in peripheral blood lymphocytes in normal subjects and in those with adenomas or colorectal cancer. The results of the study were presented at the 2010 Gastrointestinal Cancers Symposium by Sarah Kraus, PhD, lead investigator and research laboratory head at Tel Aviv Souraski Medical Center in Israel. The study was deemed to represent a promising advance in

colorectal cancer diagnosis,

and it was one of four studies included in an press cast released prior to the meeting

.

Kraus’s study initially recruited 150 consecutive patients (cohort 1) undergoing colonoscopy at the Tel Aviv Souraski Medical Center, during which peripheral blood lymphocytes were isolated from blood samples and assessed for CD24 protein expression. Among this cohort, 68 had normal colonoscopies, 19 had adenomas, and 63 patients had colorectal cancer. The sensitivity (ability to accurately detect an abnormality) and specificity (ability to differentiate cancer or adenomas from other diseases) of the CD24 test for distinguishing colorectal cancer from normal subjects was 70.5% (95% confidence interval [CI], 54.8%-83.2%) and 83.8% (95% CI, 74.6%-92.7%), respectively. For the detection of advanced adenomas, CD24 had a sensitivity of 84.2% (95% CI, 60.4%-96.4%) and specificity of 73.5% (95% CI, 61.4%-83.5%).

The researchers conducted a second validation trial, which included 73 consecutive subjects (cohort 2). Of these subjects, 38 had normal colonoscopies, 24 had adenomas, and 11 had colorectal cancer. The sensitivity of the CD24 blood test for detecting colorectal cancer was higher in this cohort than in cohort 1, at 92.3% (95% CI, 63.9%-98.7), but the specificity was similar. The specificity for detecting adenomas, however, was higher in cohort 2 than in cohort 1, at 89.2% (95% CI, 74.6%-96.9%).

Because CD24 appears to be elevated in the majority of colorectal cancer cases and adenomas, a CD24

blood test may help identify “the patients at risk for colorectal cancer and could help guide the best use of colonoscopy resources,” noted Kraus. In addition,

“[

CD24] may be a very reliable marker…for follow-up for patients who have previously had cancer” as a means of monitoring recurrence, noted

press cast moderator,

Robert P. Sticca, MD, chairman, Department of Surgery, and professor, University of North Dakota School of Medicine and Health Sciences.

Kraus noted that larger studies are needed to validate the findings before the CD24 blood test can be widely used for colorectal cancer screening, but if the test is brought to market, it is expected to be relatively inexpensive, costing about $50. The test’s economical feasibility, paired with the willingness of most patients to take a blood test, may make it an ideal tool for colorectal cancer screening, and one that may ultimately have a considerable impact on colorectal cancer outcomes.

2010 GI Symposium Abstract 286