What are PD-L1 Immunotherapy Tests?
PD-L1 Immunotherapy Tests are laboratory tests that measure the amount of PD-L1 (programmed death-ligand 1) protein expressed on cancer cells and, in some cases, immune cells within the tumor environment. PD-L1 is a protein that can help cancer cells avoid detection by the immune system. Some cancer treatments, known as immune checkpoint inhibitors, work by blocking the interaction between PD-L1 and its immune system partner, allowing immune cells to better recognize and attack cancer cells.
PD-L1 testing is commonly performed using immunohistochemistry (IHC) on a tumor tissue sample. The results can help healthcare providers determine whether a patient may be eligible for certain immunotherapy treatments. The specific scoring system and cutoff used depend on the type of cancer and the immunotherapy being considered.
How is the Test Performed?
Preparation
- Fasting is usually not required, unless you are going to have local anesthesia; then you might have to fast for several hours before the test.
- You might have to stop taking medicines such as blood thinners, as instructed by your healthcare provider.
- Inform your healthcare provider about your cancer diagnosis and previous treatments.
- Tell your healthcare provider about any previous biopsies or tumor tissue samples or if you’re pregnant.
- Follow any instructions provided before a biopsy or other tissue collection procedure.
Collection
- A tissue sample may be collected during a biopsy or surgery.
- Previously collected tumor tissue may sometimes be used, depending on its quality and suitability for testing.
- The sample is preserved and sent to a pathology laboratory for analysis.
- The procedure and preparation requirements depend on how the tissue sample is obtained.
Lab Analysis
The tumor tissue is analyzed using immunohistochemistry (IHC) to determine the amount of PD-L1 protein present. Results may be reported using scoring systems such as the Tumor Proportion Score (TPS) or Combined Positive Score (CPS), depending on the type of cancer and test used.
The results are interpreted alongside the cancer type, stage, pathology findings, and other biomarkers to help healthcare providers determine whether immunotherapy may be an appropriate treatment option.
What are the Symptoms that Prompt these Tests?
PD-L1 Immunotherapy Tests are generally performed after a cancer diagnosis to determine whether a tumor may respond to certain immunotherapy medicines. The test is not usually ordered based on symptoms alone.
Situations That May Prompt These Tests
Your healthcare provider may recommend PD-L1 Immunotherapy Tests if you have:
- Newly diagnosed cancer for which immunotherapy may be considered
- Advanced or metastatic cancer
- Recurrent cancer
- Cancer that has progressed after previous treatment
- A tumor type for which PD-L1 testing is routinely used to guide therapy
- A need to determine eligibility for immune checkpoint inhibitor treatment
Conditions That May Require These Tests
PD-L1 Immunotherapy Tests may be used to evaluate cancers such as:
- Non-small cell lung cancer (NSCLC)
- Melanoma
- Breast cancer
- Head and neck cancers
- Gastric cancer
- Gastroesophageal junction (GEJ) cancer
- Urothelial bladder cancer
- Cervical cancer
Other cancers where PD-L1 expression may influence treatment decisions
What are Normal Ranges for These Tests?
The PD-L1 immunotherapy normal range depends on the type of cancer, testing method, and scoring system used. Unlike standard blood tests, PD-L1 testing does not have one universal normal range.
Results are generally reported as a score or category.
Tumor Proportion Score (TPS)
The TPS represents the percentage of viable tumor cells showing PD-L1 staining.
- 0%: No PD-L1 expression detected on tumor cells.
- 1% to 49%: PD-L1 expression detected.
- 50% or higher: High PD-L1 expression in certain cancers, such as some cases of NSCLC.
Combined Positive Score (CPS)
The CPS considers PD-L1 staining on both tumor cells and certain immune cells within the tumor. The interpretation of a CPS result depends on the specific cancer type and treatment being considered. Different therapies may use different cutoff values.
“The reference ranges vary depending on the laboratory and the methodology used. Individuals must consult their healthcare provider for correct interpretation of the results.”
What Happens if Test Results Show Abnormal Findings?
Abnormal PD-L1 Immunotherapy Test results indicate that PD-L1 expression has been detected in the tumor.
High PD-L1 Expression
A high PD-L1 score may indicate that the cancer is more likely to respond to certain immune checkpoint inhibitors.
Depending on the cancer type, treatment may involve medicines that target immune checkpoints such as:
- PD-1
- PD-L1
- CTLA-4
However, a high PD-L1 result does not guarantee that immunotherapy will work.
Low or Negative PD-L1 Expression
A low or negative result means that little or no PD-L1 expression was detected using the test.
This may reduce the likelihood that certain immunotherapy treatments will be recommended, but it does not always rule out immunotherapy. Treatment decisions depend on:
- Cancer type
- Cancer stage
- Specific PD-L1 score
- Other biomarkers
- Previous treatments
- Overall health
Inconclusive Results
An inconclusive result may occur if:
- The tissue sample contains too few cancer cells.
- The sample is damaged or insufficient for testing.
- The tumor sample is not suitable for the selected testing method.
Your healthcare provider may recommend repeat testing or analysis of another tumor sample.
Depending on the results, additional investigations may include HER2 Tumor Marker Testing, BRAF Genetic Testing, EGFR Mutation Testing, ALK Gene Testing, KRAS Mutation Testing, or comprehensive tumor genomic profiling.
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