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Bottom line: HERmark is a powerful new test for patients who need to resolve an unclear HER2 result.
There are situations in which the standard ways of analyzing HER2 fail to provide a clear positive or negative result, leaving it uncertain as to whether or not to prescribe Herceptin (trastuzumab).
If this describes your situation, realize that it is critical that you accurately determine your tumor's HER2 status. Patients who are HER2-positive have a significantly worse prognosis. On the other hand, Herceptin is a powerful drug that essentially neutralizes the survival disadvantage caused to HER2 overexpression. In other words, if your tumor will respond to Herceptin, you need to know that.
So regarding HER2 testing, there are two situations to avoid. The first is wrongly diagnosing a patient as HER2-negative and not giving her Herceptin. The second is wrongly diagnosing a patient as HER2-positive and subjecting her to possible side effects without providing any benefit.
Today there isn't enough clinical evidence to recommend using HERmark instead of IHC. There might be in the future. So in what situation might a patient consider asking about HERmark?
1) If IHC gives an "equivocal" result (a score of 2+). Today FISH is commonly used in these cases, but HERmark is another option. Given the importance of knowing HER status with certainty, another reasonable but more expensive option in this situation might be "do both."
2) If neither IHC or FISH deliver a clear positive or negative result, or if they give conflicting ("discordant") results.
3) If a patient is determined to be HER2-negative but their disease is progressing more rapidly than expected, then consider rechecking HER2 with HERmark to make sure that the situation can't be reversed with Herceptin.
So how does HERmark differ from IHC and FISH? Remember that IHC analyzes the amount of HER2 protein on tumor cells in a "semi-quantitative" way. FISH looks at amplification of the HER2 gene, which is what causes the overabundance of HER2 protein.
HERmark, like IHC, looks at the protein. It actually looks at total HER2 protein and it looks at the extent to which HER2 proteins are paired up with each other ("homodimers"). To quantitatively assess both, it uses a method that is more sophisticated than IHC. So you get more quantitative information about HER2 status. For example, instead of knowing that your HER2 result was a "3", you might see that it was barely a three (really almost a 2). Or you might see that it was a strong 3. This might make a difference with regard to treatment approach or decisions about the value of additional HER2 testing. The point is, IHC only delivers 4 results: 0+, 1+, 2+ and 3+. HERmark tells you the real, numerical result.
As I mentioned, HERmark also does something tricky. Remember that HER2 only sends a grow signal when it is paired with either another HER2 (called a "homodimer") or with a different HER (called a "heterodimer"). HERmark tells you to what extent HER2 is found as active homodimers on the cell.
Today, the company that developed HERmark doesn't emphasize the homodimer information on the lab report. I spoke to someone at the company--Dr. Weidong Huang, an MD/PhD in their clinical research group--about this. Apparently the homodimer information isn't yet providing much value beyond the quantitative total HER2 information in the test report. The company is developing next-generation versions of the test that will look at all of the possible HER2 pairings and Dr. Weidong believes that those tests could provide key information that could bear upon treatment strategy in the future.
In a nutshell, HERmark is a powerful option for patients who need to resolve an unclear HER2 result. This is no small issue, given the importance of correctly identifying patients who will receive a drug as potent as Herceptin. The technology behind the test has strong validation. The company that developed the test, Monogram Biosciences (South San Francisco, CA) was recently purchased by LabCorp, the largest testing lab in the United States. So the experts at LabCorp obviously see great promise in the HERmark technology.
A few other details: the test takes seven days to perform, it requires a standard FFPE breast biopsy sample (FFPE is an acronym describing the way biopsy samples are most commonly stored), and it is performed at a single lab in South San Francisco. The price is $3,350. Assistance with insurance reimbursement is provided by the company.
Thanks to Dr. Weidong Huang and Bruce Nita, both of whom work for Monogram Biosciences (LabCorp).
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