1. Fuerst, Mark L.

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SAN FRANCISCO-A liquid biopsy test that identifies circulating tumor cells present in the bloodstream can detect early-stage colorectal cancer with up to 88 percent accuracy, according to a new study.

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This study is one of the first clinical studies to show that circulating tumor cells can be useful for detecting early stages of colorectal cancer. Most prior studies using circulating tumor cells have been able to detect late-stage colorectal cancer.


"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 author Wen-Sy Tsai, MD, PhD, Assistant Professor, Linkou Chang Gung Memorial Hospital, Taipei, Taiwan. "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."


Tsai presented the results of the study at the 2018 ASCO Gastrointestinal Cancers Symposium, held Jan. 18-20 (Abstract 556).


Study Methodology, Results

The prospective clinical study was conducted over a period of more than 3 years at Chang Gung Memorial Hospital, Taoyuan, Taiwan. The researchers enrolled 620 people over age 20 years who were coming to the hospital for routine colonoscopies or had a confirmed colorectal cancer diagnosis. Based on the colonoscopy and biopsy, 438 people were found to have either adenomatous polyps or early-stage to late-stage colorectal cancers. The remaining 182 study participants had no signs of a pre-cancerous growth or colorectal cancer.


All 620 enrollees had 2 mL of blood tested for circulating tumor cells analysis through a routine blood draw. The blood samples were processed using an assay that captures rare circulating tumor cells, including those found in early-stage cancer, on a lipid-coated chip that mimics human tissue. The results of these assays were then compared in a blinded analysis with the colonoscopy results.


In prior studies, this assay was found to be able to detect very small numbers of circulating tumor cells, even down to the level of one circulating tumor cell per billion blood cells found in most polyps.


The researchers found that the accuracy of the test was high and ranged from 84 percent to 88 percent between pre-cancerous and cancerous samples. The accuracy was superior to that of fecal occult blood testing.


The test had a sensitivity of 84 percent among the 182 study participants without adenomas or colorectal cancer, 76.6 percent for participants with adenomatous polyps, and 86.9 percent for patients with colorectal cancer.


"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. The specificity values were 97.3 percent, indicating a very low (less than 3%) probability of a false-positive result.


Co-author Ashish Nimgaonkar, MD, Gastroenterologist and Medical Director in the Center for Bioengineering Innovation and Design at Johns Hopkins University, Baltimore, said: "Recent surveys have found that over 80 percent of patients who are reluctant to undergo colonoscopy screening would be receptive to a blood test over stool-based tests. A number of studies have found that affordability was the number one reason for not being screened; however, this test is highly affordable and can potentially cost less than $100."


Colonoscopy would still be the gold-standard diagnostic test and be needed for tumor or polyp sample removal if an individual had a positive circulating tumor cells test, said Nimgaonkar.


Continued Research

The researchers plan to validate the use of circulating tumor cells testing in the general population in Taiwan and conduct studies in the U.S. The technology used in this study potentially could be used with other solid tumors, such as breast, lung, and prostate cancer as well.


They also noted that a simple blood draw required for the test can be easily integrated into a patient's routine physical, increasing test compliance.


ASCO Expert Nancy Baxter, MD, commented: "Screening for colorectal cancer can be life-saving, 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."


Mark L. Fuerst is a contributing writer.