Chemotherapy is the use of drugs to kill cancer cells. Unlike radiation therapy and surgery, which are localized treatments, chemotherapy is a systemic treatment. This means that the drugs travel throughout the whole body. This means chemotherapy can reach cancer cells that may have spread, or metastasized, to other areas.

Chemotherapy is rarely used to treat thyroid cancer. It is almost exclusively used when other treatments have failed. If chemotherapy is used, it may be combined with external radiation therapy.

Examples of chemotherapy drugs that may be used to treat thyroid cancer include:

  • Bleomycin
  • Dacarbazine
  • Docetaxel
  • Doxorubicin
  • Paclitaxel
  • Platinum-based agents

Researchers are still trying to determine what the benefit of chemotherapy is for various stages of thyroid cancer and its metastases. In general, surgery is more important, as is radioablation therapy. When thyroid cancer is unresponsive to these types of treatment, however, chemotherapy with or without external radiation therapy may be tried.

If the thyroid cancer is a highly aggressive form, chemotherapy may improve survival time. Doxorubicin is the most effective single agent in this type of cancer, and it is often combined with radiation treatment.

In general, the elderly and those with liver and kidney diseases are more likely to have adverse side effects. Therefore, chemotherapy drugs should be used with caution in these populations.

Chemotherapy can cause many side effects, such as:

  • Damage to bone marrow
  • Infertility
  • Lung conditions
  • Heart conditions
  • Kidney conditions
  • Conditions affecting the nervous system
  • Nausea and vomiting
  • Hair loss
  • Diarrhea
  • Bleeding in the gastrointestinal tract
  • Altered taste or smell
  • Mouth sores

Researchers continue to develop and study different strategies to slow or stop the growth of tumors. For example, a drug called vandetanib has been approved by the Food and Drug Administration (FDA) to treat medullary thyroid carcinoma (MTC). Vandetanib is designed to block the action of certain cell receptors, like the vascular endothelial growth factor (VEGF) receptor. By blocking these receptors, the drug may be able to slow or stop cancer from spreading, as well as shrink tumors.

There are a range of drugs that also inhibit growth factor receptors. The drug cabozantinib, for instance, interferes with the process that cancer cells go through to create new blood vessels, which are needed for the cancer to grow. Other treatments that are being studied include:

  • Pazopanib
  • Axitinib
  • Sunitinib

Another example of targeted therapy includes a drug called vemurafenib. This medicine is designed to treat cancer in people who have a certain mutation in a gene called the BRAF gene. Treatment with vemurafenib has show promise in slowing cancer growth and improving mortality.