Kadcyla can work in people diagnosed with HER2-positive metastatic breast cancer that has previously been treated with Herceptin and a taxane chemotherapy.
Metastatic breast cancer is breast cancer that has spread to other parts of the body away from the breast, such as the bones or liver.
Four tests can be used to find out if breast cancer is HER2-positive. To have been previously treated with Herceptin, one or more of these tests was used to determine whether or not the cancer was likely respond:
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."
Results on the IHC test may vary from lab to lab, and some labs are more competent at HER2 testing than others. Talk to your doctor about whether you want to get a FISH test, especially if you have a 1+ or 2+ result from IHC.
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 abnormal HER2 genes. This test is the most accurate, but less available, way to find out if a breast cancer 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").
SPoT-Light HER2 CISH (Subtraction Probe Technology Chromogenic In Situ Hybridization)
The SPoT-Light HER2 CISH test looks for HER2 genes in a breast cancer tissue sample. It was approved by the U.S. Food and Drug Administration in 2008. The SPoT-Light test uses a stain that makes HER2/neu genes change color. The stain is applied to the breast cancer tissue sample and looked at with a microscope. This shows how many copies of the HER2 gene are in tumor cells. The SPoT-Light test is less complicated than the FISH or IHC tests. The SPoT-Light test can be used on fresh tissue samples or tissue samples that have been stored in wax or other chemicals, but it doesn't work on frozen tissue samples.
With the SPoT-Light test, you get a score of either "positive" or "negative."
Inform HER2 Dual ISH (In Situ Hybridization)
The Inform Dual ISH test uses a special stain that makes HER2 proteins change color. The stain is applied to the breast cancer tissue sample and looked at with a microscope. The Inform HER2 Dual ISH test can be used on tissue samples that have been stored in wax or other chemicals. The Inform HER2 Dual ISH test offers more precise results than the IHC HER2 test. It is also less expensive and doesn’t need the special microscope of the FISH HER2 test.
With the Inform HER2 Dual ISH test, you get a score of either “HER2 positive” or “HER2 negative.”