Biomarker Testing for Gastric Cancer
What are gastric and GEJ cancer biomarkers?
This page includes information about biomarkers for cancers of the stomach and the gastroesophageal junction (GEJ), which begins where the esophagus meets the stomach.
Biomarkers are substances in blood, tumor or other tissue that can give doctors clues for treating cancer. Testing for are performed in a lab. tests that are performed on blood are sometimes called liquid biopsies. The results may help doctors understand:
- how fast the cancer is growing
- which treatments are most likely to work
- whether or not the cancer is responding to treatment or growing
- whether or not the cancer has come back after remission
How are gastric and GEJ cancer biomarkers used?
tests may be used to select treatments, figure out if a current treatment is working, look for early signs of recurrence, and to help patients avoid side effects from treatments that will not work for them. See our treatment page for information on the treatments available based on results.
Biomarkers for gastric and GEJ cancer treatment selection
Testing gastric or GEJ cancer for biomarkers is an important part of treatment planning especially for people with advanced cancer. These tests are used to identify cancers that may respond better to certain targeted therapies or immunotherapies and to match people to clinical trials studying new treatments.
All gastric cancers should be tested for and mismatch repair deficiency
Experts recommend testing all gastric cancers for biomarkers called (MSI), mismatch repair (MMR). These tests look at how well cancer cells can fix certain types of damage. The results of MSI and MMR testing provide similar information and may be used interchangeably.
Microsatellite testing and reporting
Microsatellite test results are usually reported in one of the following ways:
- (microsatellite instability-high)
- MSI-L (microsatellite instability-low)
- MSS (microsatellite stable)
Mismatch repair testing and reporting
Mismatch repair results may be reported in the following ways:
- mismatch repair deficient ( or )
- mismatch repair proficient (pMMR or MMR-P). Mismatch repair proficient cancers may also be called mismatch repair intact.
Why is this testing important?
Doctors often use these tests to select the best treatment for people with . People with or gastric cancers may respond well to a type of known as an .
All gastric cancers should be tested for PD-L1
is a protein that helps cancer cells avoid detection by the immune system. Experts recommend testing all newly-diagnosed gastric cancers for this .
Why is testing important?
People whose tumors express may be more likely to benefit from certain drugs called immune checkpoint inhibitors.
How are results reported?
PD-L1 results are commonly reported using a Combined Positive Score (CPS), which looks at how much protein is found in the cancer cells and nearby immune cells. For , a CPS of ≥ 1 is considered positive. The higher the CPS score, the more likely the benefit from drugs.
HER2 testing for advanced cancers
What is (Human Epidermal Growth Factor Receptor 2)?
HER2 is a protein found on the surface of some cancer cells. Tumors that make too much are called .
Why is testing important?
HER2-positive gastric cancers may respond to the targeted therapies, Herceptin (trastuzumab) and Enhertu (trastuzumab deruxtecan).
CLDN18.2 testing for advanced cancers
CLDN18.2 (Claudin 18.2) is a protein found on the surface of some cells. Current guidelines recommend testing advanced or gastric cancer for this . Tumors that make too much CLDN18.2 are called CLDN18.2-positive.
To be classified as CLDN18.2 positive, at least 75% of the tumor cells in the sample must have moderate to high levels of the CLDN18.2 protein. Because this is strict cutoff, some tumors that have some CLDN18.2 protein can still be reported as negative.
Why is testing important?
People whose tumors test CLDN18.2-positive and may be eligible for treatment with the Vyloy (zolbetuximab) in combination with chemotherapy.
Other biomarkers
TMB ()
This measures how many mutations a tumor has. Tumors with a high TMB (10 or more mutations per megabase) may be treated with the Keytruda (pembrolizumab) after other treatments, when no other alternatives remain.
NTRK gene fusions
NTRK gene fusions are biomarkers that are rarely found in . Targeted therapies to NTRK (larotrectinib, entrectinib, repotrectinib) may be used for advanced cancers of many types, including , that have progressed or have no other alternative treatments.
RET gene fusions
RET gene fusions are biomarkers that are rarely found in . The selpercatinib may be used for advanced cancers with a RET fusion that have progressed or have no other alternative treatments.
Other biomarkers
Researchers are studying new biomarkers to improve treatment outcomes for people with . See the research section below for more information.
Tumor testing vs. genetic testing
The biomarkers above are tested in the tumor itself and are not inherited. Separately, some stomach cancers are linked to an .
Sometimes tumor testing provides a clue that suggests there may be an present. When that happens, a doctor may recommend inherited genetic testing and/or referral to a genetics expert. See our section on Genetic Testing for more information.
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In the News
|
Name |
When Used |
How Used |
How Results Are Reported |
Additional Information |
|
Microsatellite stability (MSI), or |
At diagnosis for all stages of gastric and GEJ cancers. |
To determine benefit of immunotherapies |
Microsatellite testing |
Prevalence varies by age, ethnicity, , location and subtype. These biomarkers are commonly found in cancers of people with . |
|
At diagnosis for all stages of gastric and GEJ cancers. |
To determine benefit of immunotherapies, higher scores are associated with higher potential benefit. |
Combined Positive Score ≥ 1 |
Common in . Results vary depending on how the test was performed. |
|
|
Used for advanced and gastric and GEJ cancers. |
To determine the benefit of HER2-directed targeted therapies. |
About 10-15% of advanced cancers. Repeat testing on a new sample after progression or recurrence may be helpful as status can change. |
||
|
CLDN18.2 |
Used for advanced and gastric and GEJ cancers. |
To determine the benefit of CLDN18.2-directed targeted therapies. |
CLDN18.2-positive - 75% or more of the tumor cells have moderate-to-strong staining |
About 38% of advanced cancers. |
|
NTRK gene fusions |
Used for advanced and solid tumors with limited treatment options. |
To determine the benefit of targeted therapies for NTRK gene fusions. |
NTRK fusion-positive |
Rare. |
|
RET gene fusions |
Used for advanced and solid tumors with limited treatment options. |
To determine the benefit of targeted therapies for RET gene fusions. |
RET gene fusion-positive |
Rare. |
|
TMB |
Used for advanced and solid tumors with limited treatment options. |
To determine the benefit of . |
- 10 or more mutations/megabase |
Often overlaps with . |
Minimal residual disease testing
Minimal residual disease () testing is a type of . It uses a blood sample to look for tiny amounts of tumor that may remain in the body after treatment and could signal that cancer is still present somewhere in the body. Researchers are studying whether testing can help predict and find recurrence and guide treatment decisions in gastric and GEJ cancer. is still being studied in gastric and GEJ cancers and is not currently used as a routine part of care for these types of cancer.
Broader gene testing (NGS) and liquid biopsy
Next-generation sequencing (NGS) is a lab method that checks many genes at once from a single tumor sample. It is worth considering for advanced disease, since it can pick up several of the biomarkers above together and can identify clinical trial options.
If there is not enough tumor tissue, or a person is not well enough for a repeat biopsy, a blood-based test that looks for abnormal from tumors in the the bloodstream (circulating tumor or ) may be used instead. A negative result does not rule out a , because some tumor will not shed enough into the blood to be measured. Whenever possible, testing tumor tissue is the preferred starting point.
Tissue samples for testing
testing uses tumor tissue from a biopsy or surgery, so having enough good-quality tissue matters. Care teams often try to collect several biopsy samples so that all recommended tests can be completed without a repeat procedure. Some results take one to three weeks; treatment is sometimes started before all results return so that care is not delayed. Occasionally a repeat biopsy is necessary if the sample is insufficient for testing or if the cancer comes back or gets worse after treatment.
Does insurance cover the cost for gastric testing?
Most private health insurers cover standard testing in patients with who meet established medical criteria. Coverage for each test may vary based on the of cancer and which test is ordered. Insurers may cover the cost for additional testing, especially in people with advanced cancers, however, out-of-pocket costs may vary depending on the type of test. Visit our sections on insurance and reimbursement for more information.