What is a PDL1 test?
This test measures the amount of PDL1 on cancer cells. PDL1 is a protein that helps keep immune cells from attacking nonharmful cells in the body. Normally, the immune system fights foreign substances like viruses and bacteria, and not your own healthy cells. Some cancer cells have high amounts of PDL1. This allows the cancer cells to "trick" the immune system, and avoid being attacked as foreign, harmful substances.
If your cancer cells have a high amount of PDL1, you may benefit from a treatment called immunotherapy. Immunotherapy is a therapy that boosts your immune system to help it recognize and fight cancer cells. Immunotherapy has been shown to be very effective in treating certain types of cancers. It also tends to have fewer side effects than other cancer therapies.
Other names: programmed death-ligand 1, PD-LI, PDL-1 by immunohistochemistry (IHC)
What is it used for?
PDL1 testing is used to find out if you have a cancer that may benefit from immunotherapy.
Why do I need a PDL1 test?
You may need PDL1 testing if you've been diagnosed with one of the following cancers:
High levels of PDL1 are often found in these, as well as some other types of cancer. Cancers that have high levels of PDL1 can often be treated effectively with immunotherapy.
What happens during a PDL1 test?
Most PDL1 tests are done in a procedure called a biopsy. There are three main types of biopsy procedures:
- Fine needle aspiration biopsy, which uses a very thin needle to remove a sample of cells or fluid
- Core needle biopsy, which uses a larger needle to remove a sample
- Surgical biopsy, which removes a sample in a minor, outpatient procedure
Fine needle aspiration and core needle biopsies usually include the following steps:
- You will lay on your side or sit on an exam table.
- A health care provider will clean the biopsy site and inject it with an anesthetic so you won't feel any pain during the procedure.
- Once the area is numb, the provider will insert either a fine aspiration needle or core biopsy needle into the biopsy site and remove a sample of tissue or fluid.
- You may feel a little pressure when the sample is withdrawn.
- Pressure will be applied to the biopsy site until the bleeding stops.
- Your provider will apply a sterile bandage at the biopsy site.
In a surgical biopsy, a surgeon will make a small cut in your skin to remove all or part of a breast lump. A surgical biopsy is sometimes done if the lump can't be reached with a needle biopsy. Surgical biopsies usually include the following steps.
- You will lie on an operating table. An IV (intravenous line) may be placed in your arm or hand.
- You may be given medicine, called a sedative, to help you relax.
- You will be given local or general anesthesia so you won't feel pain during the procedure.
- For local anesthesia, a health care provider will inject the biopsy site with medicine to numb the area.
- For general anesthesia, a specialist called an anesthesiologist will give you medicine so you will be unconscious during the procedure.
- Once the biopsy area is numb or you are unconscious, the surgeon will make a small cut into the breast and remove part or all of a lump. Some tissue around the lump may also be removed.
- The cut in your skin will be closed with stitches or adhesive strips.
There are different types of biopsies. The type of biopsy you get will depend on the location and size of your tumor.
Will I need to do anything to prepare for the test?
You won't need any special preparations if you are getting local anesthesia (numbing of the biopsy site). If you are getting general anesthesia, you will probably need to fast (not eat or drink) for several hours before surgery. Your surgeon will give you more specific instructions. Also, if you are getting a sedative or general anesthesia, be sure to arrange for someone to drive you home. You may be groggy and confused after you wake up from the procedure.
Are there any risks to the test?
You may have a little bruising or bleeding at the biopsy site. Sometimes the site gets infected. If that happens, you will be treated with antibiotics. A surgical biopsy may cause some additional pain and discomfort. Your health care provider may recommend or prescribe medicine to help you feel better.
What do the results mean?
If your results show your tumor cells have high levels of PDL1, you may be started on immunotherapy. If your results do not show high levels of PDL1, immunotherapy may not be effective for you. But you may benefit from another type of cancer treatment. If you have questions about your results, talk to your health care provider.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a PDL1 test?
Immunotherapy does not work for everyone, even if you have tumors with high levels of PDL1. Cancer cells are complex and often unpredictable. Health care providers and researchers are still learning about immunotherapy and how to predict who will benefit the most from this treatment.
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