Will Tykerb Work for You?
Tykerb can work in people with advanced HER2-positive breast cancers that have stopped responding to anthracyclines, taxanes, and Herceptin.
Two tests are used to find out if the breast cancer is HER2-positive. These tests are given before Herceptin is prescribed. The IHC test measures HER2 receptor protein, and the FISH test counts copies of the HER2 gene:
- IHC (ImmunoHistoChemistry)
IHC is the most commonly used test to see if a tumor has too much of the HER2 receptor protein on the surface of the cancer cells.
The IHC test gives a score of 0 to 3+ that indicates the amount of HER2 receptor protein in tumors. If the tumor scores 0 to 1+, it's called "HER2 negative." If it scores 2+ or 3+, it's called "HER2 positive."
The IHC test results are most reliable for fresh or frozen tissue samples. IHC tends to be an unreliable way to test tissue that's preserved in wax or other chemicals. FISH testing is the preferred way to assess preserved tissue samples.
- FISH (Fluorescence In Situ Hybridization)
The FISH test looks for the HER2 gene abnormality. This test is the most accurate, but less available, way to find out if a breast tumor is HER2-positive. The FISH test shows how many copies of the HER2 gene are in tumor cells. The more copies of the gene, the more HER2 receptors the cells have.
With the FISH test, you get a score of either "positive" or "negative" (some hospitals call a negative test "zero").