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What is biomarker testing?

In the cancer world, biomarker testing helps healthcare providers learn more about cancer by looking for proteins, genes and other substances (called biomarkers) from cancer cells. Some cancers contain biomarkers that might indicate what is driving the cancer and help oncologists determine which cancer treatments can be most effective.

Biomarker testing is different from genetic testing. It does not look for inherited genes that may increase a person’s risk of developing cancer. Biomarker testing is for people who already have cancer to help select cancer treatments. It can be done on certain types of blood cancer and solid tumors. Biomarker testing is sometimes referred to as tumor testing, tumor genetic testing, genomic testing, genomic profiling, molecular testing, molecular profiling, somatic testing, or tumor subtyping.

Why do biomarker testing?

The results of your biomarker test can lead your healthcare provider to a targeted therapy known to work for the biomarkers found in your test. The matching therapy may be available as an FDA-approved treatment, an off-label targeted therapy, or through a clinical trial.

For patients with metastatic (stage IV) non-small cell lung cancer (NSCLC) whose biomarker test discovers the ROS1 gene fusion or rearrangement, the preferred first line treatment is a targeted therapy – also known as a tyrosine kinase inhibitor (TKI). TKIs are more effective than chemotherapy and generally have fewer side effects.

How is biomarker testing done?

Biomarker testing is done using a sample of cancer cells taken either through a biopsy or as part of a surgery for tumor removal. The sample is sent to a lab where they identify and document all of the biomarkers found within the cancer cells. In some cases, biomarker testing can be done using cancer cells or parts of cancer cells found in blood or other fluids.

With some biomarker testing that includes genes, you may also need to supply a sample of healthy cells. These are typically found in saliva, blood or skin. Healthy cells are compared to the cancer cells to determine differences in the genetic makeup of the cancer cells. In solid tumor cancers, healthy cells are not needed to determine what is driving the cancer growth and are rarely collected for biomarker testing but may be collected for research purposes.

How is ROS1 discovered in biomarker testing?

ROS1+ cancer can only be discovered when your tumor tissue, fluid from a pleural effusion, or a blood sample is sent for biomarker testing. Currently, ROS1 is tested for and found primarily in patients who have lung cancer; however, the ROS1 biomarker has been found in many other cancers, including melanoma, sarcoma, breast and brain cancer.

Are there different kinds of biomarker testing?

There are many different types of biomarker testing. Some tests look for a single biomarker, whereas others check for many different types of biomarkers in a single sample.

National Comprehensive Cancer Network (NCCN) Guidelines recommend, at this time, biomarker testing for metastatic NSCLC be performed via a broad, panel-based approach that looks for many (or even hundreds) of biomarkers. A few of the tests that can identify ROS1+ cancer include:

  • Next Generation Sequencing (NGS). An NGS test platform is capable of detecting ROS1 fusions and provides information about multiple biomarkers in a single test. An NGS test can be done with a tissue or liquid biopsy and can screen for a broad range of mutations.

  • Fluorescence in situ hybridization (FISH). FISH uses “break-apart” probes to detect certain ROS1 gene rearrangements. However, this test is not able to distinguish between different fusion variants.

  • ROS1 fusions can also be detected using other methods such as immunohistochemistry (IHC) or reverse transcription polymerase chain reaction (RT-PCR).

Talk to your healthcare provider to discuss which biomarker testing is best for your particular cancer.

When should I have biomarker testing?

Health care providers suggest biomarker testing after a patient is diagnosed with certain types of cancer. Biomarker testing is suggested for anyone diagnosed with metastatic non-small cell lung cancer, breast cancer, or colorectal cancer, and other cancers as determined by health care professionals.

However, diagnosis is not the only time biomarker testing is useful. Additional biomarker testing is also suggested for people with cancer that has spread or come back after treatment. Many ROS1ders who have metastatic cancer experience progression of their disease when treatment stops being effective. In these cases, biomarker testing can be helpful in determining next steps and other treatments available for advanced cancer.

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