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Should I Test My Tumor? Why Biomarker Testing is Important for Cancer Treatment

🕐 8 min read

(BPT) – A new medicine approved by the U.S. Food and Drug Administration (FDA) is part of an exciting evolution in the way doctors treat cancer. Traditionally, cancer is treated based on where it starts in the body, but now doctors can treat some cancers based on specific genetic rearrangements, or biomarkers, that cause the cancer to grow – regardless of the organ or tissue from which it originates. This is known as tumor-agnostic treatment.1

Biomarker testing is different from genetic testing, which looks for traits inherited from your mother or father found in every cell of your body and then determines if you have higher risk of developing cancer or other diseases. Biomarker testing, however, is done after a cancer diagnosis to find genetic changes that occur in the tumor itself and can help doctors make treatment decisions.2,3

For example, biomarker testing can identify a genetic rearrangement called neurotrophic tyrosine receptor kinase (NTRK) gene fusions, which can be found in certain advanced solid tumors, including common cancers like breast and colorectal cancers as well as rare tumor types. Rates of NTRK vary based on the type of cancer, occurring in less than 1 percent of colorectal cancer cases and up to 100 percent of some rare salivary gland cancers.4 If a person’s tumor is found to be NTRK gene fusion-positive, they may be eligible to receive a targeted medicine such as Rozlytrek™ (entrectinib), which was recently approved by the FDA.

“Rozlytrek is the most recent advance in tumor-agnostic medicine, which is providing personalized treatment options that target the unique genetic makeup of each person’s cancer,” said Dr. Robert Doebele, Associate Professor of Medicine, Division of Medical Oncology, University of Colorado. “Through biomarker testing, we can potentially unlock information that can have an important impact on determining their options for treatment.”

Here is what you need to know about biomarker testing:

What is biomarker testing?

Biomarker testing identifies changes within your cancer cells that cause your tumor to grow. In addition to NTRK, there are other biomarkers, such as ROS1, ALK, BRAF, EGFR, HER2, PD-L1 and many more, that testing may reveal and that can be matched to different medicines. Tests either search for biomarkers one at a time or can identify a wide range at once.

Who should have biomarker testing?

Anyone diagnosed with an advanced cancer should ask their doctor about biomarker testing. It is the only way to identify if you could potentially benefit from certain medicines, so it is a critical part of the conversation that takes place with your care team to find the right treatment.

It’s important to note that not everyone who gets tested will have tumors that have an identifiable biomarker that can be targeted with a medicine. However, the test may reveal potential treatment options that are available based on your specific cancer.

When should I have a conversation about biomarker testing with my doctor?

It’s best to talk to your doctor about biomarker testing as soon as you learn you have advanced cancer. If your doctor thinks testing is right for you, testing will be done as soon as possible following your diagnosis and prior to treatment.

Where does biomarker testing take place?

Depending on the location of your tumor and type of test, biomarker testing can be done at a doctor’s office, hospital or testing facility.

How is biomarker testing done?

A healthcare professional, such as your doctor, will collect a small sample from your tumor and send the sample to a lab. A laboratory technician will scan your tumor’s genetic information to find any biomarkers and communicate the findings to your doctor, who will share the results with you and help you to understand what they mean for decisions around your treatment.

Rozlytrek™ U.S. Indication (pronounced roz lye’ trek)

Rozlytrek is a prescription medicine used to treat:

  • Adults with non-small cell lung cancer (NSCLC) that has spread to other parts of the body and is caused by an abnormal ROS1 gene
  • Adults and children 12 years and older with solid tumors (cancer) that:
    • are caused by certain abnormal NTRK genes and
    • have spread or if surgery to remove their cancer is likely to cause severe complications, and
    • there is no satisfactory alternative treatment option or the cancer grew or spread on other treatment

It is not known if Rozlytrek is safe and effective for use in children less than 12 years of age.

Rozlytrek was approved in NTRK gene fusion-positive solid tumors through a faster FDA review process based on the percentage of patients whose tumor size shrank or disappeared after treatment and how long that response lasted. There are ongoing studies to confirm benefit of Rozlytrek for this use.

Important Safety Information

Rozlytrek may cause serious side effects, including:

  • Congestive heart failure. Rozlytrek may cause congestive heart failure or make the congestive heart failure that a patient already has worse. Patients should tell their healthcare provider right away if they have any of the following signs and symptoms of congestive heart failure:
    • persistent coughing or wheezing
    • trouble breathing when lying down
    • sudden weight gain
    • increasing shortness of breath
    • tiredness, weakness, or fatigue
    • swelling in ankles, feet, or legs
  • Central nervous system (CNS) effects. Rozlytrek may cause dizziness, changes in mood, or may affect how a patient thinks and cause confusion, hallucinations, and problems with concentration, attention, memory, and sleep. Patients should tell their healthcare provider right away if they have any of these symptoms.
  • Bone fractures. Rozlytrek may increase the risk of bone fractures. Bone fractures may happen with or without a fall or other injury. Patients should tell their healthcare provider if they have pain, changes in movement, or bone abnormalities.
  • Liver problems (hepatotoxicity). A healthcare provider will do blood tests to check a patient’s liver function during treatment with Rozlytrek. Patients should tell their healthcare provider right away if they develop symptoms of liver problems including: loss of appetite, nausea or vomiting, or pain on the upper right side of the stomach area. A healthcare provider may temporarily stop treatment, decrease the dose, or permanently stop Rozlytrek if a patient develops liver problems with Rozlytrek.
  • Increased uric acid level in the blood (hyperuricemia). Rozlytrek may cause an excess of uric acid in the blood. A healthcare provider may do tests before and during a patient’s treatment with Rozlytrek to check the uric acid level in the blood. A healthcare provider may prescribe medications if a patient has high blood uric acid levels.
  • Changes in the electrical activity of the heart called QT prolongation. QT prolongation can cause irregular heartbeats that can be life-threatening. A healthcare provider will do tests before and during treatment with Rozlytrek to check the electrical activity of the heart and body salts (electrolytes). Patients should tell their healthcare provider right away if they feel faint, lightheaded, dizzy, or feel their heart beating irregularly or fast while taking Rozlytrek. These may be symptoms related to QT prolongation.
  • Vision problems. Rozlytrek may cause vision problems. Healthcare providers may stop Rozlytrek and refer to an eye specialist if a patient develops severe vision problems during treatment with Rozlytrek. Patients should tell their healthcare provider right away if they have any loss of vision or any change in vision, including:
    • double vision
    • blurry vision
    • new or increased floaters
    • seeing flashes of light
    • light hurting the eyes

Before taking Rozlytrek, patients should tell their healthcare provider about all their medical conditions, including if they:

  • have liver or kidney problems.
  • have any heart problems, including a condition called long QT syndrome.
  • have nervous system (neurological) problems.
  • have or have had eye or vision problems.
  • are pregnant or plan to become pregnant. Rozlytrek can harm an unborn baby. Patients should tell their healthcare provider right away if they become pregnant during treatment with Rozlytrek or think they may be pregnant.
    • If patients are able to become pregnant, their healthcare provider will do a pregnancy test before they start treatment with Rozlytrek.
    • Females who are able to become pregnant should use effective birth control during treatment with Rozlytrek and for at least 5 weeks after the final dose.
    • Males who have female partners that are able to become pregnant should use effective birth control during treatment with Rozlytrek and for 3 months after the final dose.
  • are breastfeeding or plan to breastfeed. It is not known if Rozlytrek passes into breast milk. Do not breastfeed during treatment with Rozlytrek and for 7 days after the final dose of Rozlytrek. Patients should talk to their healthcare provider about the best way to feed their baby during this time.

Patients should tell their healthcare provider about all the medicines they take, including prescription and over-the-counter medicines, vitamins, or herbal supplements.

Certain other medicines may affect how Rozlytrek works causing side effects. Patients should know the medicines they take. Patients should keep a list of them to show to their healthcare provider and pharmacist when they get a new medicine.

The most common side effects of Rozlytrek include:

  • tiredness
  • constipation
  • change in taste
  • swelling
  • dizziness
  • diarrhea
  • nausea
  • abnormal touch sensation
  • shortness of breath
  • muscle pain
  • confusion, mental status changes, memory problems, and hallucinations
  • weight gain
  • cough
  • vomiting
  • fever
  • joint pain
  • vision changes

These are not all the possible side effects of Rozlytrek. For more information, patients should ask their healthcare provider or pharmacist.

Patients should call their doctor for medical advice about side effects.

Report side effects to the FDA at (800) FDA-1088 or Report side effects to Genentech at (888) 835-2555.

Please see for the full Prescribing Information, including Patient Information.


1 Flaherty KT, Le DT, Lemery S. Tissue-Agnostic Drug Development. Am Soc Clin Oncol Educ Book. 2017;37:222-230. doi: 10.14694/EDBK_173855. Accessed April 2019.

2 National Comprehensive Cancer Network; Biomarker Testing; [internet] Accessed May 2019.

3 National Institute of Health, Genetics Home Reference; What is Genetic Testing; [internet] Accessed May 2019.

4 Amatu A, Sartore-Bianchi A, Siena S. ESMO Open. 2016;1(2):e000023. PMID: 27843590

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