AACR-NCI-EORTC: Colorectal Cancer Test Could Detect Early Cancer-Causing Genetic Biomarkers With High Degree of Sensitivity

Key Points

  • For all tissue samples, ColoScape detected mutations with 95% specificity and 91% sensitivity. For tissue samples that excluded adenomas, ColoScape detected mutations with 96% specificity and 100% sensitivity.
  • For plasma samples that excluded adenomas, ColoScape detected mutations with 92% specificity and 86% sensitivity. In tests that combined tissue and plasma, with adenomas excluded, specificity and sensitivity were both 93%.
  • A previous study indicated that the panel could detect precancerous lesions with over 65% accuracy in stool samples.

An investigational test that screens for colorectal cancer could detect genetic mutations that are indicative of the disease with a high degree of sensitivity and specificity, according to results of a study presented by Powell et al at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, held October 26–30 in Philadelphia (Abstract LB-11).

“Early detection of colorectal cancer dramatically increases rates of patient survival,” said the study’s lead author, Michael J. Powell, PhD, C.Chem, MRSC, Chief Scientific Officer of DiaCarta Inc. “Currently, available molecular tests for colorectal cancer do not detect early cancer or adenomas with enough sensitivity and specificity.”

ColoScape Screening

Current colorectal cancer guidelines suggest that patients of average risk get screened regularly from age 50 to age 75. Colonoscopy and fecal occult blood tests are the most common screening tools.

The ColoScape assay can be used as a screening assay. However, Dr. Powell explained that its primary use is as a triage, recurrence, and monitoring assay. The ColoScape assay uses xenonucleic acid (XNA) molecular clamping technology to detect multigene mutation biomarkers in colorectal cancer. Dr. Powell explained that XNAs are novel synthetic analogs of nucleic acids that help suppress the amplification of normal DNA sequences and allow selective amplification of mutated DNA sequences using real-time polymerase chain reaction (qPCR).

Study Findings

In this validation study, researchers analyzed a total of 324 clinical samples from tissue biopsies and plasma. For all tissue samples, ColoScape detected mutations with 95% specificity and 91% sensitivity. For tissue samples that excluded adenomas, ColoScape detected mutations with 96% specificity and 100% sensitivity.

For plasma samples that excluded adenomas, ColoScape detected mutations with 92% specificity and 86% sensitivity. In tests that combined tissue and plasma, with adenomas excluded, specificity and sensitivity were both 93%.

Dr. Powell added that a previous study, led by DiaCarta’s collaborators at the University of Potsdam in Germany, from which the biomarker panel was licensed, indicated that the panel could detect precancerous lesions with over 65% accuracy in stool samples.

Future of ColoScape

If the ColoScape test is approved, it would be available commercially as an in vitro diagnostic kit, which could be used in a local hospital setting or laboratory with qPCR capabilities. Dr. Powell said that since the test can be performed in local hospitals or labs, it could potentially make molecular testing more accessible to patients. ColoScape can be used to study tissue, stool, or plasma samples. Results can be obtained in 3 to 4 hours, compared with about 2 weeks for competing screening technology, according to Dr. Powell.

Dr. Powell said that if ColoScape is approved by the U.S. Food and Drug Administration, it would typically be administered after a patient had a positive fecal hemoglobin test or at the recommendation of a physician. If the patient tested positive for the mutations that can indicate colorectal cancer, he would receive a follow-up colonoscopy. DiaCarta anticipates that the assay could also be used to monitor patients following surgery or chemotherapy, as the presence of certain biomarkers could suggest a recurrence of colorectal cancer.

Dr. Powell said that by identifying the mutations associated with colorectal cancer, ColoScape could help clinicians determine how to treat each patient. For example, he noted, a patient with a BRAF mutation might receive a targeted therapy that has shown benefit in patients with that specific mutation.

DiaCarta is currently seeking further clinical validation for the ColoScape assay in the United States and China, and intends to seek regulatory approvals for the test in all those markets. ColoScape currently is approved for in vitro diagnostic use in Europe (CE-IVD).

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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