I am going to post some info about the question of HER2 scoring because so many here may not know the answer. However, I still can't answer the question of how significant it might be to have FISH results that are more definitely positive in terms of how well trastuzumab or lapatinib works.
Here's past posts and info:
Here's one source:
http://www.breastcancer.nzco.net/herceptinFAQ.htm
5. What is the FISH test?
The Fluorescence In Situ Hybridization test illuminates the HER2 genes in the tumour sample to see how many there are. If a FISH test detects more than 2 copies of the HER2 gene, this means that the cell is abnormal and the breast cancer is called "FISH positive" which also means the cancer is now called "HER2 positive". These women are also more likely to benefit from Herceptin®. If "FISH negative", then the women will not benefit from Herceptin®.
Here's a better one, from a post on the her2support.org site, by Al, who does a lot of research:
HER2 testing
Tests can be done to find out whether a woman has HER2-positive breast cancer. Testing can be done at the same time as initial breast cancer surgery, or samples of cancer tissue from previous biopsies, or surgery, may be used.
The two main methods used for testing are
Immunohistochemistry (IHC) and
Fluorescence in-situ hybridization (FISH):
Immunohistochemistry (IHC)
Immunohistochemistry (IHC) can show how much of the HER2 protein is present in the tumour sample. The HER2 level is graded from 0 to 3+
- 0–1+ means that a normal amount of the HER2 protein is present and the result is HER2-negative.
- 2+ means that a moderate amount of the HER2 protein is present.
- 3+ means that there is a higher than normal level of HER2 protein and the result is HER2-positive.
When a tumour is scored at 2+, UK testing guidelines recommend that an extra test is carried out. This is because a result of 2+ does not always mean a cancer cell has a high level of HER2. In this situation, an extra test (known as FISH) is used to give a definite result.
Fluorescence in-situ hybridization (FISH)
Whereas IHC measures the level of HER2 protein in the tumour sample, FISH testing measures the amount of the HER2/neu gene in each cell. This gene is responsible for the overproduction of the HER2 protein.
There is no number scale for FISH testing. The result is either:
- FISH negative - normal levels of the gene are present, or
- FISH positive – excessive amounts of the gene are present. This is sometimes called gene amplification.
http://www.cancerbacup.org.uk/Cance...sis/HER2testing