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Study of Cabozantinib in Adults with Progressive Thyroid Cancer Who Did Not Respond to Previous Treatment with Radioactive Iodine and VEGFR Therapy

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on patients with radioiodine-refractory differentiated thyroid cancer that has continued to grow after previous treatment. The condition occurs when thyroid cancer cells no longer respond to standard radioactive iodine therapy and have progressed despite prior treatments targeting blood vessel growth.

The study will test a medication called cabozantinib (also known as XL184) compared to placebo. The medication is given as film-coated tablets that are taken by mouth. The purpose is to determine if cabozantinib can slow down or stop cancer growth in patients whose disease has worsened after previous therapy.

During the study, participants will be randomly assigned to receive either cabozantinib tablets or placebo tablets. Neither the patients nor their doctors will know which treatment they are receiving. The treatment may continue for up to 51 months, with regular medical check-ups to monitor the patient's condition. The study will track how long it takes for the cancer to progress and measure if the tumors shrink in response to treatment.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial medication assignment

    You will be randomly assigned to receive either cabozantinib tablets or placebo tablets

    If assigned to cabozantinib, you will receive either 20 mg or 60 mg film-coated tablets for oral use

    The tablets should be taken by mouth as prescribed

  2. Step 2

    Regular health monitoring

    Your thyroid hormone levels will be regularly checked to ensure they remain below 0.50 mIU/L

    Regular blood tests will monitor your organ function and blood cell counts

    Imaging scans will be performed to track any changes in your thyroid cancer

  3. Step 3

    Ongoing treatment requirements

    Continue taking thyroid hormone replacement therapy as prescribed

    Use effective birth control methods during the study and for 4 months after the last dose

    Report any side effects or health changes to the medical team

  4. Step 4

    Regular assessments

    Complete quality of life questionnaires about your mobility, self-care, usual activities, pain/discomfort, and anxiety/depression

    Undergo regular imaging scans to measure tumor response

    Provide blood samples for research purposes, including measurement of tumor markers

  5. Step 5

    Study completion

    The study is expected to continue until July 2026

    Follow-up visits will be scheduled after treatment completion

    Final assessments will evaluate the medication's effectiveness and safety

Who can join the trial?

13 criteria

  • Must be 16 years or older at the time of giving consent
  • Must have confirmed thyroid cancer that has been verified through tissue examination
  • Must be receiving thyroid hormone therapy with specific blood test requirements within 28 days before study start
  • Must be able to understand and follow study requirements and sign informed consent (for those under 18, parent/guardian consent is required)
  • Must have measurable disease on CT or MRI scan within 28 days before study start
  • Must have previously received treatment with radioactive iodine or been deemed unsuitable for this treatment
  • Must have previously received treatment with at least one specific type of targeted therapy (lenvatinib or sorafenib)
  • Must have evidence that the disease has progressed during or after previous treatment
  • Must have recovered from side effects of any previous treatments
  • Must have good physical functioning status (ECOG score of 0 or 1, meaning able to perform daily activities)
  • Must have adequate blood cell counts and organ function based on laboratory tests
  • For women who can become pregnant: must not be pregnant and must agree to use effective birth control during the study and for 4 months after
  • For men: must agree to use barrier contraception (like condoms) unless they have had a vasectomy

Who cannot join the trial?

15 criteria

  • Age below 18 years old
  • History of severe allergic reactions to cabozantinib or similar medications
  • Pregnant or breastfeeding women
  • Active or untreated brain metastases (cancer that has spread to the brain)
  • Significant heart problems, including:
    • Uncontrolled high blood pressure
    • Heart attack within the last 6 months
    • Unstable heart rhythm disorders
    • Severe liver problems
    • Severe kidney problems
    • Major surgery within 2 months before starting the study
    • Currently participating in another clinical trial
    • Any condition that, in the opinion of the doctor, would make it unsafe to participate in the study
    • Unable to swallow pills
    • History of bleeding problems
    • Active infections requiring systemic treatment (medications that affect the whole body)
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Investigated drugs

  • Cabozantinib

    (also known as XL184) is a medication that targets specific proteins called VEGFRs (vascular endothelial growth factor receptors) that are involved in cancer growth. It works by blocking signals that cancer cells use to grow and spread. This medication is being studied as a treatment for patients with thyroid cancer that no longer responds to radioactive iodine therapy and has continued to grow after previous treatments.

  • Placebo

    is an inactive substance that contains no medication. It is used as a comparison to measure the true effectiveness of the active medication being tested in the study.

  • Radioiodine

    (RAI) therapy, while not directly tested in this trial, is mentioned as a previous standard treatment that patients in this study no longer respond to. It is a type of radiation therapy that uses radioactive iodine to treat thyroid cancer.

What is already known about the treatment

Cabozantinib – A targeted oral medication used in the treatment of advanced thyroid cancer, specifically for patients whose cancer has become resistant to radioactive iodine therapy and has progressed after previous treatments. It works by blocking specific proteins called tyrosine kinases, particularly VEGFR (Vascular Endothelial Growth Factor Receptor), which are involved in cancer cell growth and blood vessel formation. The drug belongs to the class of tyrosine kinase inhibitors and is administered in tablet form, taken once daily. Cabozantinib has shown effectiveness in clinical trials for improving progression-free survival in patients with differentiated thyroid cancer who have exhausted other treatment options.

Investigated diseases

Thyroid Cancer - A disease that develops in the thyroid gland, which is located in the front of the neck. It begins when healthy thyroid cells undergo changes and grow out of control, forming a mass or tumor. The condition can progress from early stages where the cancer is confined to the thyroid gland to more advanced stages where it spreads beyond the thyroid. Differentiated thyroid cancer, which develops from follicular cells, is the most common type. In some cases, the cancer may become resistant to traditional radioiodine therapy, a condition known as radioiodine-refractory thyroid cancer.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-516478-31-00Protocol codeXL184–311Estimated enrolment197 patientsSponsorExelixis Inc.

sourced from the EU Clinical Trials Register and site verification

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