I HER2 GA
Gastric and gastroesophageal junction (GEJC) cancer;
Technical component (TC) avaialble
Paraffin embedded tissue block
3 slides (3-5 uM) per marker on adhesion glass
If submitting HER2 protein over-expression by immunohistochemistry,
HER2(ERBB2) gene amplification by in situ hybridization or estrogen /
progesterone receptor expression by immunohistochemistry, the specimen must
follow fixation guidelines listed below:
1. Specimens should be immersed in fixative within one hour of the biopsy or
2. If delivery of a resection specimen to the pathology department is delayed (eg,
specimens from remote sites), the tumor should be bisected prior to the
immersion in fixative. In such cases, it is important that the surgeon ensure
that the identity of the resection margins is retained in the bisected specimen;
alternatively, the margins may be separately submitted.
3. The time of removal of the tissue and the time of immersion of the tissue in
fixative should be recorded and submitted to the laboratory.
Ship ambient. Protect from extreme temperature with an ice pack. Separate ice pack from specimen.
Inadequate fixation; Improper labeling
An IHC score of 3+ or a positive FISH result (HER2/CEP17 ratio greater or equal to 2.0) provides eligibility for Herceptin. Patients with IHC scores of 0/1 should not be treated with Herceptin. IHC score of 2+ should be retested using FISH. Any equivocal cases should be retested by an alternate method.
The FDA recently approved trastuzumab (Herceptin, Genentech) for use in combination with cisplatin and capecitabine or 5-fluorouracil to treat patients with human epidermal growth factor receptor 2 (HER2)-over expressing (also called HER2-positive) metastatic gastric or GEJC who have not received prior treatment for metastatic disease.
The new indication was largely based upon the results of the “Trastuzumab for Gastric Cancer” or ToGA trial (Lancet. August 28, 2010). The trial revealed that patients on trastuzumab plus chemotherapy had a median overall survival of 13.8 months compared to 11.1 months with chemotherapy alone. However, stratifying the HER2+ group into two subgroups (a) FISH+ and IHC-negative (IHC0 or IHC1+) vs. (b) IHC3+ or ICH2+FISH+ revealed more distinct 11.8 month and 16.0 month median overall survivals, respectively. FISH-positivity alone did not indicate Herceptin benefit; Herceptin benefit was essentially limited to immunohistochemically 3+ gastric cancers or IHC2+ and FISH+ cancers.
IHC or FISH can be used as the first-line testing method, but based on ToGA data and pending future investigations, oncologists should consider immunohistochemistry for optimal frontline testing.