HER2-Positive Gastric Cancer: Testing, Meaning and Treatment
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What Is HER2-Positive Gastric Cancer?
HER2-positive gastric cancer is a type of stomach cancer where tumor cells have higher-than-normal levels or extra copies of the HER2 protein or gene. HER2 (human epidermal growth factor receptor 2) is a protein on cell surfaces that helps control cell growth and division. In these cancers, HER2 is either overproduced or the gene is amplified, which can make the cancer more aggressive. HER2 status is determined by testing tumor tissue from a biopsy or surgery using standardized lab techniques. A diagnosis of HER2-positive means the tumor meets set criteria for HER2 overexpression or gene amplification.
What Is HER2 in Gastric Cancer?
HER2 (also called HER2/neu or ERBB2) is part of a family of receptors that help send signals for cell growth. In some gastric cancers, the HER2 pathway is abnormally active due to:
- Protein overexpression: Too much HER2 protein on the cell surface.
- Gene amplification: Extra copies of the HER2 (ERBB2) gene in tumor DNA. HER2 positivity is most often found in gastric adenocarcinoma, the most common type of stomach cancer.
Why Is HER2 Testing Done?
HER2 testing helps guide treatment decisions, especially for people with advanced, recurrent, or inoperable gastric cancer. If the tumor is HER2-positive, it may be eligible for targeted treatments that specifically block HER2. Not all gastric cancers are HER2-positive, so testing ensures therapies are matched to the right patients.
How Is HER2 Testing Performed?
- Immunohistochemistry (IHC): The main method. Tumor tissue is stained and scored from 0 to 3+:
- 0–1+: HER2-negative
- 2+: Borderline (“equivocal”), needs more testing
- 3+: HER2-positive
- In Situ Hybridization (ISH/FISH): Checks for extra copies of the HER2 gene, used if IHC is 2+ to clarify status.
Interpreting HER2 Test Results:
- Positive:IHC 3+ or IHC 2+ with gene amplification (ISH/FISH) means HER2-positive.
- Negative:IHC 0–1+, or IHC 2+ without gene amplification, means HER2-negative.
- Equivocal:IHC 2+ with no ISH result—needs more tests.
HER2-Positive vs HER2-Negative Gastric Cancer:
- HER2-positive tumors:Show overexpression or amplification and may be treated with HER2-targeted drugs.
- HER2-negative tumors:Not eligible for HER2-targeted therapy but may receive chemotherapy, immunotherapy (depending on other markers), or other targeted agents.
HER2 status is only one factor in choosing treatments. Prognosis depends on stage, health, response to therapy, and other biomarkers.
HER2-Targeted Treatments:
For eligible patients, therapies that block HER2 (like monoclonal antibodies) can improve survival in advanced gastric cancer. Treatment is personalized based on disease stage, prior therapies, HER2 expression, and other factors.
Can HER2 Status Change?
Yes, HER2 status can vary within a tumor and over time. It may change after treatment or at relapse, so new testing might be needed if the treatment plan depends on updated HER2 status.
Key Points: HER2 is a growth-regulating protein; HER2-positive gastric cancer has too much of this protein or extra gene copies. Testing uses IHC and, if needed, ISH/FISH. Results are classified as positive, negative, or equivocal. HER2-positive patients may be eligible for HER2-targeted therapy; others receive alternative treatments. HER2 status can change, especially after treatment, so retesting may sometimes be needed.
FAQs on HER2-Positive Gastric Cancer
What does HER2-positive mean?
High HER2 protein or gene amplification, which may allow for targeted therapy.
How is HER2 tested?
Mainly by IHC, with ISH/FISH for borderline cases.
Difference between HER2-positive and HER2-negative?
HER2-positive may get targeted drugs; HER2-negative relies on other therapies.
What does the result mean for treatment?
HER2-positive can get HER2-targeted therapy; HER2-negative will have other options.
Is HER2 testing for all patients?
It’s recommended for advanced or metastatic cases, but not always for early-stage cancers.