Research led by Johns Hopkins University in collaboration with the University of Pittsburgh shows that colon cancer-specific antigen-2 (CCSA-2) may be an accurate indicator of colorectal cancer. CCSA-2 is a tumor marker (a substance found in a person's blood, urine, or body tissue that may indicate an abnormal process in the body; also called a biomarker) that can be measured with a blood test.

In this study, the researchers analyzed 135 blood samples from patients who had undergone colonoscopies. A colonoscopy is a screening test for colorectal cancer that allows doctors to look inside the colon and rectum for polyps (an abnormal growth that may be precancerous; a higher-risk polyp is called an adenoma) or cancer using a colonoscope (lighted tube). The patients were diagnosed as normal (24%), having potentially precancerous growths (polyps: 19%; nonadvanced adenomas: 29%; advanced adenomas: 14%), or colorectal cancer (14%). A control group of 125 people, made up of individuals with noncancerous conditions or other types of cancer, was also included.

The CCSA-2 test had an overall specificity of about 80% (meaning that about 20% of positive results indicated that the samples were cancerous when there was no cancer) and a sensitivity of 91% (meaning that 9% of cancer cases were missed). The researchers also noted that higher levels of CCSA-2 in the blood correlated with larger precancerous growths, and the highest levels of CCSA-2 indicated colorectal cancer. So, the researchers could distinguish patients who had colorectal cancer or advanced adenomas from those with low-risk polyps or normal colons.

"With CCSA-2, we've found a biomarker that not only better detects the presence of colorectal cancer, but also may accurately indicate whether a patient has a high-risk, precancerous condition," said Eddy S. Leman, PhD, Instructor, Department of Urology at Johns Hopkins Hospital in Baltimore, Maryland.

What This Means for Patients

The goal of this research was to find an accurate, simple, and noninvasive method for the early detection of colon cancer. Although this study is promising, the test needs to be repeated with a larger group of patients at more research institutions and is not available for colorectal cancer screening at this time. Many health organizations recommend that men and women be screened for colorectal cancer beginning at age 50, or earlier if there is a strong family history of colorectal cancer or polyps. For more information on colorectal cancer screening, talk with your doctor.