Novel Blood Test Detects Colorectal Cancer Recurrence Earlier

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide, accounting for more than 600,000 deaths each year. When diagnosed early, before cancer has spread, the relative five-year survival rate for CRC is 90%, but only about 4 out of 10 CRC cases are detected early.

Among individuals undergoing surgical treatment for CRC, recurrence occurs in 30% to 40% of all cases, the majority of which present in the first two to three years following initial diagnosis and treatment. This early and concentrated pattern is relatively unusual among cancers, and offers the opportunity for structured surveillance to detect signs of recurrence.

A new blood test has been developed to detect tumor-specific methylated DNA biomarkers that may leak from active lesions into the circulatory system. Current data suggest that a genomic test specific for these biomarkers is more sensitive than carcinoembryonic antigen (CEA) testing and is highly specific. One element of the standard of care for post-surgical monitoring for CRC recurrence is quarterly or semi-annual blood-based testing to measure CEA levels, which has poor sensitivity and specificity.

Clinical Genomics (Edison, NJ, USA) has announced new data supporting its 2-gene blood test for post-surgical monitoring of colorectal cancer recurrence. In one study investigators compared the sensitivity and specificity of methylated Branched Chain Amino-Acid Transaminase 1 (BCAT1) and IKAROS Family Zinc Finger 1 (IKZF) (2-gene test) with those of CEA in blood to monitor patients for recurrence of colorectal cancer following potentially curative resection of a primary tumor. Recurrence was assessed by clinical findings and periodic computed tomographic surveillance scans.

The presence in blood of either methylated BCAT1 or IKZF1 or elevated CEA was considered positive for recurrence. Interim study results reflect data from 120 patients with known recurrence status (30 recurrences confirmed via imaging or other clinical means; 90 patients with no evidence of recurrent CRC). Overall sensitivity estimates for recurrence were 63% (19/30) for methylated BCAT1/IKZF1 versus 23% (7/30) for CEA. Specificity estimates in the 90 patients with no evidence of disease were 86% for methylated BCAT1/IKZF1 versus 96% for CEA. No cases with confirmed recurrence were CEA positive only.

The authors of the studied concluded that their results demonstrate that BCAT1 and IKZF1 are highly methylated in colorectal cancer tissue with low methylation levels in surrounding non-tumor tissue, suggesting that these methylated genes are highly tumor-specific without a field effect. The presence of methylated BCAT1 and IKZF1 in blood appears to be related to tumor invasiveness, enabling tumor access to the bloodstream. The studies were presented on January 23, 2016, at the American Society of Clinical Oncology 2016 Gastrointestinal Cancers Symposium (ASCO GI) held in in San Francisco (CA, USA).

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