The word biomarker is a combination of the words “biology” and “markers”. They are measurable features, such as proteins and genes, found in your blood and tumour tissue that give doctors a clearer picture of your cancer.
Biomarkers could reveal how your cancer might behave, what makes it unique, and which treatments may benefit you the most.
Biomarkers are a rapidly evolving area of cancer care. You may also hear other terms used to describe this area, including:
- Molecular testing/profiling
- Genomic testing
- Somatic testing
- Tumour testing
- Precision/personalized medicine
All of these terms mean that more information is being gathered about your cancer, and that this information can help guide treatment based on its unique features.
How do biomarkers inform my care?
Biomarkers provide important information that helps guide your care at every stage.
They can help with:
- Diagnosis: confirming the type of cancer.
- Classification: classifying the cancer type further (gene mutations, molecular features, etc.)
- Prognosis: predicting how the cancer may grow or change over time
- Treatment planning: guiding decisions about options and timing
- Monitoring: tracking changes in the cancer and how the body responds to treatment
- Risk and prevention: identifying genetic differences that may increase cancer risk for you and your family.
Sometimes, biomarkers can have multiple roles across all of these stages, and therefore they are often grouped by function:
- Diagnostic biomarkers – these biomarkers can help identify the type of cancer.
- Predictive biomarkers – these biomarkers can help predict the response a person will have to certain treatments.
- Prognostic biomarkers – these biomarkers can help predict how the cancer will evolve and behave (the disease outcome).
When should I have biomarker testing?
You could have biomarker testing at various points throughout your care.
Biomarker testing may be appropriate:
- at diagnosis
- when planning treatment to prevent a recurrence
- if the cancer comes back
- when considering clinical trials
Some biomarker tests are done automatically at the time of diagnosis. This is called reflex testing. You can work with your doctor to decide how much detail you would like to receive about your results, and when.
It is possible that your tumour’s biomarkers may change over time. Ask your doctor if you should be retested.
What biomarkers are relevant to ovarian cancer?
There are multiple biomarkers relevant to ovarian cancer. The following table includes examples of biomarkers that are relevant to ovarian cancer treatment (this is not a complete list):
What learn from this biomarker:
- Looks to see whether the BRCA 1 and BRCA 2 genes, which help repair damaged DNA, are working properly.
- If these genes are not working properly, this test also checks to see if this change was inherited from a biological parent ( “germline” or inherited) or if it only exists in the tumour (“somatic” or not inherited).
How this biomarker informs treatment:
- Helps predict if PARP inhibitor medications like olaparib (Lynparza) and niraparib (Zejula) are likely to work well.
- It can also show whether a person may be at higher risk for other cancers and whether cancer risk may run in the family. This information is important because it can help inform effective prevention strategies.
How often it’s used:
- Commonly tested (standard of care).
Diagnostic, predictive, prognostic?
- Predictive, prognostic, and diagnostic.
What learn from this biomarker:
- Looks to see whether cancer cells can properly repair DNA (regardless of having a BRCA mutation).
How this biomarker informs treatment:
- Helps identify patients who may benefit from PARP inhibitor medications like olaparib (Lynparza) and niraparib (Zejula).
How often it’s used:
- Tested in some cases.
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks to see whether cancer cells can repair small mistakes in its DNA.
How this biomarker informs treatment:
- Helps predict whether the patient is likely to benefit from immunotherapy, such as pembrolizumab (Keytruda).
- It can also show whether the person may have Lynch Syndrome, revealed through subsequent genetic testing.
How often it’s used:
- Tested in some cases.
Diagnostic, predictive, prognostic?
- Predictive, prognostic.
What learn from this biomarker:
- Looks for a protein (folate receptor alpha) on cancer cells that can be targeted by specific treatments.
How this biomarker informs treatment:
- Helps identify patients who may benefit from the medication mirvetuximab soravtansine (Elahere).
How often it’s used:
- Tested in some cases.
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks for a protein called HER2 on the surface of cancer cells.
How this biomarker informs treatment:
- Helps determine whether certain targeted therapies, such as trastuzumab (Herceptin), may be used in a clinical trial setting.
How often it’s used:
- Mainly used in clinical trials; not standard of care.
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks for changes in genes that can cause cancer cells to grow in abnormal ways. These changes are often found in low-grade serous ovarian cancer.
How this biomarker informs treatment:
- Helps identify patients with low grade serous ovarian cancer who may benefit from MEK inhibitors, such as trametinib (Mekinist) and avutometinib in combination with defactinib.
How often it’s used:
- Becoming more common in low grade serous ovarian cancer but not routinely used for other types of ovarian cancers.
Diagnostic, predictive, prognostic?
- Predictive.
What biomarkers are relevant to endometrial cancer?
What learn from this biomarker:
- Looks to see if the cancer is able to repair small mistakes in its DNA.
How this biomarker informs treatment:
- Helps predict if the patient is likely to benefit from immunotherapy, such as pembrolizumab (Keytruda).
- Can also show whether the person may have Lynch Syndrome (which puts them at higher risk for other cancers) and whether cancer risk may run in the family.
How often it’s used:
- Commonly tested (standard of care).
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks for changes in the POLE gene, which helps copy and repair DNA accurately.
How this biomarker informs treatment:
- POLE-mutated cancers tend to have a good prognosis and may be treated with surgery alone.
How often it’s used:
- Testing is becoming more common, as it is part of classifying the molecular type of the cancer.
Diagnostic, predictive, prognostic?
- Prognostic
What learn from this biomarker:
- Looks for abnormalities in the p53 protein, which normally helps control cell growth and prevent cancer.
How this biomarker informs treatment:
- p53-abnormal cancers tend to be more aggressive and may require additional treatment, including chemotherapy and radiation.
How often it’s used:
- Testing is becoming more common, as it is part of classifying the molecular type of the cancer.
Diagnostic, predictive, prognostic?
- Prognostic
What learn from this biomarker:
- Looks to see whether cancer cells have receptors for the hormone estrogen.
How this biomarker informs treatment:
- Can help determine whether hormone therapy may be effective.
How often it’s used:
- Sometimes tested.
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks for a protein (folate receptor alpha) on cancer cells that can be targeted by specific treatments.
How this biomarker informs treatment:
- Helps identify patients who may benefit from the medication mirvetuximab soravtansine (Elahere).
How often it’s used:
- Sometimes tested.
Diagnostic, predictive, prognostic?
- Predictive.
What learn from this biomarker:
- Looks for a protein called HER2 on the surface of cancer cells.
How this biomarker informs treatment:
- Helps determine if HER2-targeted therapies, such as trastuzumab (Herceptin).
How often it’s used:
- Mainly used in clinical trials; not standard of care.
Diagnostic, predictive, prognostic?
- Predictive.
Because every person – and every cancer – is different, not all biomarkers will apply to every patient.
Speak with your doctor to better understand what is most relevant in your case.
What does biomarker testing involve?
Biomarker testing involves collecting a sample from your body.
Depending on the test, biomarker testing may involve:
- A blood or saliva test.
- A test performed on cancer tissue that was already removed during surgery.
- A test performed on a new sample of cancer tissue removed by biopsy.
How do I access biomarker testing?
How you access biomarker testing depends on where you live in Canada. Depending on which province/territory you live in, some biomarker testing may be publicly funded. Some biomarker testing may also be accessed in clinical trials, or patients may pay for biomarker testing.
Speak to your oncologist to learn what options are available to you. This is an evolving situation as research and advocacy efforts are ongoing.
Kristine's story
“When I was first diagnosed, I felt like I was suddenly expected to understand this whole new world of information… everything all at once."
“At the same time, I was trying to process the shock of my diagnosis and what it meant for me, for my family, and for my future.
I was diagnosed in May 2024 with high grade serous 3C ovarian cancer after an ultrasound found tumors on each of my ovaries. At that point, my only focus was on survival and getting through surgery and chemotherapy.
Initially I was advised about the genetic testing that I had consented to, which would determine if I carried an inherited mutation like BRCA. This was offered as part of my care. While I was BRCA negative, it was discovered I did have a genetic mutation, PMS2, which is associated with Lynch syndrome.
What really helped was being assigned to a genetic counselor who explained things along the way.
After my genetic test came back BRCA negative, my oncologist advised that they would try to get HRD testing, which would tell us more about my treatment plan and its effectiveness.
Kristine, living with ovarian cancer
At first, I didn’t even realize that HRD testing was an option in Canada. And secondly, if it was, I didn’t understand why it wasn’t automatic or standard. This all added to my confusion and uncertainty.
Eventually, my HRD test came back positive. Ironically, I received the results the day before I was starting Zejula. Even though my treatment plan wasn’t changing, having that information was comforting. It gave me confidence and hope.”
"I've come to appreciate that knowledge doesn't change the diagnosis - it can, however, change how you experience the journey."