In the upcoming months, there surely will be an increasing number of blood-based genomic cancer tests approved by the FDA. This specific test market is just too attractive. In a recent note, I discussed some of these testing initiatives from the perspective of companion diagnostics (see: An Expanding Definition for Companion Diagnostics). This form of testing in used in collaboration with cancer therapy to select the right drug or monitor the effectiveness of drug therapy. Obviously and of equal importance are biomarkers intended for cancer screening. A recent article reported that the FDA has cleared the first blood-based screening test for colorectal cancer (see: FDA Clears First Blood-Based Colorectal Cancer Screening Test), Below is an excerpt from it:
The first blood-based colorectal cancer (CRC) screening test, Epi proColon...has been approved by the US Food and Drug Administration (FDA)....The Epi proColon test is a qualitative in vitro diagnostic test for detecting methylated Septin9 DNA, which has been associated with the occurrence of CRC, in plasma obtained from whole-blood specimens. It is indicated for use in average-risk patients who have chosen not to undergo other screening methods, such as colonoscopy or stool-based tests.The test was recommended for FDA approval in 2014 by the Molecular and Clinical Genetics Panel of the FDA's Medical Devices Advisory Committee, but some of the experts were not convinced....The agency approved the Epi proColon test for CRC screening in average-risk patients (as defined by current screening guidelines) who choose not to be screened by colonoscopy or a stool-based FIT [fecal immunochemical test for occult blood in the stool].The Epi proColon blood test for CRC screening can be performed during routine office visits. It requires no dietary restrictions or alterations in medication use. The blood sample is analyzed by a local or regional diagnostic laboratory....The company will initiate a postapproval study to show the long-term benefit of blood-based CRC screening using Epi proColon, as required by the FDA.
Here's more information about Septin9 DNA (see: Plasma methylated septin 9: a colorectal cancer screening marker):
The biomarker septin 9 has been found to be hypermethylated in nearly 100% of tissue neoplasia specimens and detected in circulating DNA fractions of CRC patients. A commercially available assay for septin 9 has been developed with moderate sensitivity (∼70%) and specificity (∼90%) and a second generation assay, Epi proColon 2.0 (Epigenomics AG), shows increased sensitivity (∼92%). The performance of the assay proved to be independent of tumor site and reaches a high sensitivity of 77%, even in early cancer stages (I and II). Furthermore, septin 9 was recently used in follow-up studies for detection of early recurrence of CRC.
There is clearly a need for a blood-based biomarker for colorectal cancer screening. Patients tend to dislike the home stool collection that is required for fecal immunochemical tests for occult blood in the stool (FIT). Moreover, testing for blood in the stool offers a somewhat crude substitute for the identification of reliable cancer biomarkers in the blood. It must be noted, however, that some of the FDA experts in 2014 were not convinced that the septic 9 biomarker offered advantages over FIT.
I am not sure that septin 9 will be the final and most efficient biomarker for CRC but I am sure of two things. The first is that there will eventually be a high-specificity, high-sensitivity blood test for CRC. The second is that probably tens of billions of dollars would be saved by the elimination of screening colonoscopies for CRC by such a test. I found an article dating way back to 2002 about the number of screening endoscopies performed in the U.S. but the numbers are sill impressive (see: How many endoscopies are performed for colorectal cancer screening?) Here is a quote from it: "Approximately 2.8 million flexible sigmoidoscopes and 14.2 million colonoscopies were estimated to have been performed in 2002." Needless to say, many gastroenterologists and radiologists may be hoping that such a lab test does not reach the market soon.