Colorectal cancer is the third most common cancer found in both men and women in the U.S., and is the second leading cause of cancer deaths. Approximately 1.2 million cases of colorectal cancer are expected to occur globally.

Just last week, the FDA approved Qiagen’s Therascreen KRAS companion diagnostic to identify colorectal cancer patients most likely to respond to Amgen’s Vectibix. This approval follows a 2012 approval of the same test as a companion diagnostic for Eli Lilly’s Erbitux.

Vectibux and Erbitux both target epidermal growth factor receptors (EGFR), which is overexpressed in some types of colon cancer.

EGFR is found on the cell surface and is activated by growth factor binding. Once activated, EGFR activates enzymes inside the cell that drive the cell forward into cell division. Vectibix and Erbitux both work by inhibiting EGFR’s activation.

About 50% of colorectal patients respond well to treatment with an EGFR inhibitor. Those that do not respond usually have a mutation in a “downstream” enzyme—one of the enzymes driving cell division that is normally only activated in response to EGFR activation. One such enzyme that is commonly mutated in colon cancer is called KRAS. Therascreen detects KRAS mutations that make a patient non-responsive to EGFR inhibitors such as Vectibix and Erbitux.

Given the high cost of these drugs—up to $30,000 per eight weeks of treatment—this new companion diagnostic should be welcome by insurers and patients alike, helping to accurately treat colorectal cancer patients by eliminating a costly and time consuming drug therapy for patients who would not see any benefit from it.


A companion diagnostic is the test or measurement intended to assist physicians in making treatment decisions for their patients, usually by determining the efficacy and/or safety of a specific drug for a targeted patient group.


The Therascreen test works by taking DNA from a patient’s tumor cells and mixing it with reagents that specifically bind to and make copies of the tumor’s KRAS gene.

If a specific cancer-associated mutation is present, a fluorescent signal is released. Therascreen tests for the presence of seven specific mutations known to make EGFR inhibitors ineffective.


According to research and marketing firm GlobalData, the companion diagnostics testing market value will increase from $421 million in 2013 to $670 million by 2020.


EGFR overexpression is associated with a number of cancers, including lung cancer, anal cancers, and glioblastoma multiforme.

These somatic mutations involving EGFR lead to its constant activation, which produces uncontrolled cell division. Mutations, amplifications or misregulations of EGFR or family members are implicated in about 30% of all epithelial (tissues that line cavities and surfaces of structures throughout the body) cancers.

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