Novel CTC Assay Detects Early-Stage Colorectal Cancer

Roxanne Nelson, RN, BSN

January 23, 2018

SAN FRANCISCO — A novel assay for detecting circulating tumor cells (CTCs) holds potential as a screening test for colorectal cancer, because it detects the disease at an early stage, and even detects precancerous lesions, findings from a new study indicate.

The new blood test showed a high degree of accuracy for detecting early-stage colorectal cancer — accuracy ranged from 84% to 89% — and it is the first assay to demonstrate high sensitivity in the detection of precancerous colorectal lesions.

The assay used in this study is the CellMax biomimetic platform (CMx), developed by CellMax Life. According to the company, the CMx uses a "proprietary platform-microfluidic chip, antibody, and imaging software," which has enabled Celllife to overcome the "intractable" challenge of detecting rare CTCs in precancerous cases and in cases of early-stage disease, when cancer can be successfully treated.

The findings were presented at the Gastrointestinal Cancers Symposium (GICS) 2018.

"Colorectal cancer is among the most preventable cancers when precancerous lesions are detected at an early stage," said lead author Wen-Sy Tsai, MD, assistant professor, Linkou Chang Gung Memorial Hospital, Taipei, Taiwan. "Unfortunately, most colorectal cancer is diagnosed late, even though it can be prevented."

Despite the availability of screening methods, one third of persons in the United States have never been screened. "Current screening methods require bowel prep or are inconvenient, resulting in low compliance," said Dr Tsai. "Stool-based tests have limited sensitivity for the detection of precancerous lesions."

Study coauthor Ashish Nimgaonkar, MD, assistant professor of medicine, Johns Hopkins University, Baltimore, Maryland, pointed out that affordability has been cited as the number one reason why individuals are not being screened.

"However, this CTC test is highly affordable and can potentially cost less than $100," Dr Nimgaonkar said. He noted that colonoscopy would remain the gold-standard diagnostic test and would be needed to sample tumors or to remove polyps if the CTC test results were positive.

A simple blood test as a first step is a highly attractive idea, and assays that measure CTCs or circulating tumor DNA (ctDNA) shed from primary and metastatic cancers are being intensively studied for many different cancers. Dubbed "liquid biopsy," such assays hold the promise of providing information similar to that obtained through traditional biopsy or more invasive methods of screening.

High Accuracy in All Groups

"We have conducted a prospective clinical study over a period of more than 3 years to assess a novel assay to detect and enumerate circulating tumor cells in a blood sample for early colorectal cancer detection," said Dr Tsai.

The study, which involved 620 participants, was conducted at a single center in Taiwan. Particpants included 182 healthy control persons and 327 patients with colorectal cancer (56 with stage I; 84 with stage II; 118 with stage III; 43 with stage IV; and 26 whose disease was not staged). In addition, the study included 111 participants with precancerous lesions.

Each participant underwent a routine blood draw, which was then analyzed using the CMx. A multivariate analysis was also performed to assess the clinical performance of the assay, and disease status was evaluated by a standard clinical protocol that included colonoscopy and biopsy results.

The overall accuracy of the CMx test was 88% for all disease stages, including precancerous lesions.

The false positive rate for control persons was low, at 3.3%. The false negative rate for cancer patients was 15.8%

For the entire cohort, the sensitivity was 84.0 (95% confidence interval [CI], 80.3 - 87.2), the specificity was 97.3 (95% CI, 93.7 - 98.8), and the area under the curve (AUC) was 0.87.

Among those with precancerous lesions, the sensitivity was 76.6 (95% CI, 67.9 - 83.5), the specificity was 97.3 (95% CI, 93.7 - 98.8), and the AUC was 0.84.

For cancer patients, the sensitivity was 86.9 (95% CI, 82.8 - 90.1), the specificity was 97.3 (95% CI, 93.7 - 98.8), and the AUC was 0.88.

The next step is to validate the use of CTC testing in the general population in Taiwan and to conduct studies in the United States.

Dr Tsai added that this technology could potentially be used for screening for other solid tumors, including those of the lung, breast, and prostate.

In a discussion of the paper, Douglas Corley, MD, PhD, from Kaiser Permanente, San Francisco Medical Center, California, reiterated that the important question is whether blood tests can improve early detection of cancer.

"We are getting closer to zero deaths from colon cancer," he said, noting that screening colonoscopy has been associated with a markedly decreased risk for death from colorectal cancer.

"Circulating tumor cells for screening looks promising, especially with the low false positive rate, but must be interpreted with caution," said Dr Corley. "Interpreting new screening tests depends heavily on population tested and required replication."

In a statement, Nancy Baxter, MD, American Society of Clinical Oncology expert in gastrointestinal cancers, commented: "Screening for colorectal cancer can be lifesaving, but Americans still lag behind federal government screening goals because current screening options can be inconvenient and uncomfortable for patients. Though this research needs more investigation, a simple, accurate blood test could help increase screening rates, which could ultimately improve detection of colorectal cancers at earlier stages, when treatment is most likely to be curative."

The study was sponsored by the Ministry of Health in Taiwan and by Chang Gang Memorial Hospital. Dr Tsai has disclosed no relevant financial relationships. Dr Nimgaonkar has served in a consulting or advisory role with CellMax Life. Several coauthors also have relationships with industry, including CellMax Life.

Gastrointestinal Cancers Symposium (GICS) 2018. Abstract 556, presented January 20, 2018.

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