Not all lung cancers are the same. And a lung cancer diagnosis can differ from person to person. An important step in the assessment of your lung cancer is testing it for biomarkers. Biomarker testing, also called tumour, molecular or genomic testing, is an important part of your full diagnosis. The test looks for changes in the tumour’s DNA. It involved testing for abnormalities in its DNA and levels of specific proteins in the tumour.
Learning more about cancer’s biomarkers can be very helpful in understanding more about your type of cancer and the treatment that may work for you. If you have lung cancer (NSCLC or SCLC) it is important to discuss comprehensive biomarker testing. This looks for many genetic alterations and proteins in the genes known to be associated with lung cancer, to give doctors more information about your situation.
But What Is a Biomarker Anyway?
Certain biomarkers (mutations or presence of proteins on cells) can be the “drivers” that cause cancer to grow and spread. Doctors can test for biomarkers with a biopsy. This is where tissue is removed from a tumour, so it can be tested. Biomarker testing can also be done on tissue removed during surgery. Sometimes a doctor will use a blood test, also known as a liquid biopsy. He or she will decide which test is right for you.
Here are some of the common biomarkers you may be tested for if you have lung cancer:
- Epidermal growth factor receptor (EGFR)
- Anaplastic lymphoma kinase gene rearrangement (ALK)
- ROS1 rearrangement (ROS1)
- BRAF V600E mutation (BRAF)
- Neurotrophic tyrosine receptor kinase fusion (NTRK)
- MET amplification or MET exon 14 skipping (MET)
- Programmed death-ligand 1 (PD-L1)
- Kirsten rat sarcoma mutations (KRAS)
Why Should I Get Tested?
Testing for biomarkers can help you and your doctor decide what treatment to choose that may slow down the lung cancer growth and spread. If your lung cancer tests positive for a biomarker, you and your doctor may discuss targeted therapies or immunotherapy.
It can take up to 3 weeks to get biomarker testing results. Getting your complete results will give your doctor information to help make treatment decisions that are right for you.
There are 3 steps that are an important part of creating a treatment plan:
Step 1: TALK
Talk to your doctor about having a more complete diagnosis by testing for biomarkers before determining which treatment is right for your lung cancer.
Step 2: KNOW
Your doctor will test your lung cancer for biomarkers by sending a tissue or blood sample to a lab. Results take time but can help your doctor understand more about your specific type of cancer.
Step 3: TREAT
Biomarker test results can reveal specific information about your type of lung cancer. This will help you and your healthcare team determine which treatment options may work for you.
Biomarkers for Lung Cancer
These are some of the most important biomarkers doctors look for when making treatment decisions:
PD-L1:
PD-L1 (Programmed death-ligand 1) is a protein that helps keep the body’s immune responses under control by acting as a “brake”. PD-L1 can be found on some normal cells and in higher-than-normal amounts on certain types of cancer cells. Some cancer cells exploit an immune checkpoint process involving two cell surface molecules—PD-L1 and PD-1. They produce lots of PD-L1, which binds to PD-1 on the surface of T cells, a specific type of immune cell. When cancer cells interact with T cells in this way, they trick the immune system into identifying the cancer cells as normal cells.
At the time of diagnosis, all new lung cancer patients should have their PD-L1 levels tested.
EGFR:
EGFR stands for epidermal growth factor receptor. These are molecules found on the surface of certain cells in the body, and they transmit signals that tell these cells to grow. Some lung cancer cells contain EGFR molecules with defects or mutations that make them overactive. These defective EGFR molecules constantly signal the cancer cells to grow and divide, making the tumour larger.
In Canada, around 14% of adenocarcinomas, a subtype of NSCLC, have EGFR mutations.
K-RAS:
The K-RAS (Kirsten rat sarcoma) gene sends signals involved in regulating cell growth. K-RAS mutations are found in 15% of NSCLC patients who never smoked and 25% of patients who smoked.
BRAF:
The BRAF gene is responsible for making a specific protein called B-Raf. This protein helps send chemical signals from the outside of cells to the cell's nucleus. If mutated, BRAF genes have the potential to cause normal cells to become cancerous. Approximately 1% to 3% of NSCLCs have a BRAF mutation known as V600E.
ALK:
ALK stands for anaplastic lymphoma kinase. Some cancer cells contain ALK genes that are mixed or fused with another gene—this is known as an ALK fusion. The rearranged ALK gene produces an altered ALK molecule that promotes the growth and spread of cancer cells. ALK fusions occur in about 3% to 5% of NSCLCs. They are more common in younger people with adenocarcinoma who have never smoked or used to be light smokers. ALK inhibitors block these defective ALK molecules.
MET:
MET stands for mesenchymal-epithelial transition. The MET gene is involved in protein creation. Having extra copies of the MET gene in the body means that extra growth signals are being sent to the cancer. Having extra copies of the MET gene is relatively uncommon in lung cancer. A specific error in MET called exon 14 skipping allows the MET protein to hang around longer and send growth signals that can promote cancer.
ROS1 mutations:
The ROS1 gene makes a protein that sends signals in cells helps with cell growth. Non–small cell lung cancer that has a mutation in this gene is called ROS1 positive (ROS1+). Some cancer cells contain ROS1 genes that are mixed or fused with another gene—this is known as an ROS1 fusion. This mutation is found in only 1% of NSCLCs; like ALK mutations, it is more common in younger people, non-smokers, and light smokers.
Once you and your doctor know as much as you can about the type of lung cancer you have, you can discuss the best treatment options for you. Talk to your doctor about biomarker testing for your lung cancer.
