The results of the prospective study were released ahead of a presentation at the 2018 Gastrointestinal Cancers Symposium in San Francisco, California. The study marks the first to show a high sensitivity for detecting precancerous lesions, as prior studies tended to identify later-stage CRCs.
“Our study is important because there is still some reticence among patients to use stool-based tests or have an invasive exam like colonoscopy to detect colorectal cancer,” said lead study author Wen-Sy Tsai, MD, in a statement. “Our results may point to a solution for people who are reluctant to get an initial screening colonoscopy or are not compliant in returning stool-based test kits that they get from their doctors.”
A prospective and blinded study was conducted at the Chang Gung Memorial Hospital in Taoyuan of 620 people, including 438 patients with adenomatous polyps, or diagnosed stage I to IV CRC, and 182 healthy controls undergoing routine colonoscopies. Peripheral blood was tested from each participant, and was processed using the CellMax (CMx) biomimetic, lipid-bilayer coated microfluidic chip to capture rare CTCs. CMx can detect 1 CTC in a billion blood cells in most polyps. Results of the assay were then compared with colonoscopy and biopsy results.
Overall, the study demonstrated accuracy of 88% for detecting all stages of CRC, including precancerous lesions. Among patients with precancerous lesions (n = 111), the sensitivity was 76.6% (95% CI, 67.9%-83.5%), and there was 86.9% (95% CI, 82.8%-90.1%) sensitivity for detecting stage I-IV CRCs (n = 327). The study authors noted that the accuracy of the CTC assay was superior to that of fecal occult blood testing.
The specificity of the test was 97.3% (93.7%-98.8%) across the patient cohort, indicating a probability of less than 3% of potential false positives. “We believe our high specificity results are important because a high number of false-positive results would discourage many people who are considering getting screened for colorectal cancer from doing so,” said Tsai, assistant professor in the Department of Colon and Rectal Surgery at Linkou Chang Gung Memorial Hospital in Taipei, Taiwan.
The use of the blood-based liquid biopsy could improve low compliance with current screening methods for CRC that are more inconvenient for patients. “Recent surveys have found that over 80% of patients who are reluctant to undergo colonoscopy screening would be receptive to a blood test over stool-based tests,” co-author Ashish Nimgaonkar, MD, assistant professor of medicine, Johns Hopkins University, Baltimore, Maryland, said in a statement. “A number of studies have found that affordability was the number 1 reason for not being screened, however this test is highly affordable and can potentially cost less than $100.”
However, if a patient had a positive CTC result, a colonoscopy would be needed to test the tumor or polyp, Nimgonkar added.
Further study is planned to validate the results of the assay in the general population in Taiwan, as well as in the United States and in other solid tumors.
Tsai WS, Nimgaonkar A, Segurado O, et al. Prospective clinical study of circulating tumor cells for colorectal cancer screening. J Clin Oncol. 2018;36(suppl 4S; abstr 556).