Exploring Current Therapies for Thyroid Cancer With NTRK Mutations

Marcia Brose, MD, PhD, director of the Center for Rare Cancers and Personalized Therapy, director of the Thyroid Cancer Therapeutics Program, associate professor of Otorhinolaryngology: Head and Neck Surgery at the Hospital of the University of Pennsylvania, and associate professor of Medicine at Penn Medicine, discusses the treatment options for patients with thyroid cancer and NTRK fusions.

There are 2 FDA-approved drugs for these patients, larotrectinib (Vitrakvi) and entrectinib (Rozlytrek). Both of these therapies target TRK fusions in patients with thyroid cancer. Brose says that the fusion happens because a TRK gene fuses with another gene. When that occurs, it activates a pathway which may have caused the patient’s cancer in the first place. Physicians test for these fusions to see if they can target the abnormal pathway with one of these agents, which gives them a chance to focus on the cause of the cancer.

Larotrectinib and entrectinib inhibit this gene, and as a result stop the cancer from growing, according to Brose. For many patients, these treatments cause a significant amount of shrinkage of their cancer; in some cases, it causes so much shrinkage that the patient’s disease cannot be found. Brose says we cannot think these patients are cured because there is no data to show that, but getting the disease burden down to be small enough that it can’t be found on a CAT scan is a new level of response that hasn’t been achieved with other agents.

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