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.
Why is testing important?
People whose tumors test positive for CLDN18.2 may be eligible for treatment with the Vyloy (zolbetuximab).
Other biomarkers
NTRK gene fusions
NTRK gene fusions are biomarkers that are rarely found in . Targeted therapies may be used for different types of advanced cancers (including ) with NTRK gene fusions that have gotten worse, stopped responding or came back after other treatments.
RET gene fusions
RET gene fusions are biomarkers that are rarely found in . Targeted therapies may be used for different types of advanced cancers (including ) with RET gene fusions that have gotten worse, stopped responding or came back after other treatments.
Other biomarkers
Researchers are studying new biomarkers to improve treatment outcomes for people with . See the research section below for more information.
Participate in Research
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 |
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. |
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.
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.