San Diego, CA, May 23, 2016—Measuring natural killer cell activity (NKA) with a simple new blood test may help identify patients at risk for colorectal cancer (CRC), according to research presented here at Digestive Disease Week 2016.
“Natural killer cells are actually the first line of defense against viruses, bacteria, tumor cells, that are swimming around in your body. Natural killer cells are the first ones to come and attack, who see that these cells are foreign in the body, and start attacking. As they attack these foreign cells, they also call in the adoptive immune system, such as T cells, to come and help them kill foreign cells,” explained Katia Betito, PhD, vice president, scientific affairs, ATGen Canada, Inc. “There is a large body of data—decades old—to show that natural killer cell activity is low in a number of disease states, such as cancer.”
Gilles Jobin, MD, FRCPC, department of medicine, University of Montreal, Montreal, Quebec, Canada, and fellow researchers undertook this study in patients with CRC and adenomatous polyps (AP) to evaluate the sensitivity, specificity, positive and negative predictive values of the in vitro diagnostic device (IVDD; ATGen Canada Inc.), which measures NKA in blood.
For this study, blood was drawn from 762 subjects presenting for CRC screening or prescribed colonoscopies on the day of colonoscopy, prior to the procedure. Dr. Jobin and colleagues found statistically significant differences in the NKA of the 21 patients who tested positive for CRC and the 741 patients who tested negative (CRC mean: 344.2 pg/mL, SD: 881.7; CRC-negative mean: 731.5 pg/mL, SD: 1019.3, P=0.001; CRC median: 87.9 mg/mL, IQR: 49.0-151.0; CRC-negative median: 294.8 pg/mL, IQR: 98.7-895.5; P ≤ 0.001).
These researchers also found a prevalence of 2.8% for CRC, and 13.4% for AP ≥ 10 mm. Upon conducting receiver operator characteristics (ROC) analysis, they found that the optimum cut-off for the detection of CRC was 181.3 pg/mL (AUC: 71%).
The sensitivity of the IVDD in detecting CRC was 85.7% at a cut-off of 200 pg/mL, a specificity of 59.6%, positive predictive value of 5.7%, and negative predictive value of 99.3% (see Table 1). At a cut-off of 500 pg/mL, IVDD for detection of AP ≥ 10 mm, in a statistical analysis of 102 patients, had a sensitivity of 56.9%, a specificity of 35.0%, positive predictive value of 11.9%, and negative predictive value of 84.0%.
“If somebody is negative on this test, there is a very high likelihood that they won’t have cancer, that they will be healthy,” noted Dr. Betito.
What is the bottom line for clinicians?
“This is a very different way of looking at a risk assessment for CRC; it measures something different than the fecal test. The fecal test measures blood in stool. We measure the activity in your innate immune system, which is very different,” said Dr. Betito. “It’s another tool in your armament of what you have available to decide ‘What is the risk that my patient might have CRC?’” Dr. Betito concluded.