What`s new in thyroid cancer research and treatment?
Important research into thyroid cancer is being done right now in many university hospitals, medical centers, and other institutions around the country. Each year, scientists find out more about what causes the disease, how to prevent it, and how to improve treatment. In past years, for example, evidence has grown showing the benefits of combining surgery with radioactive iodine therapy and thyroid hormone therapy. The results include higher cure rates, lower recurrence rates, and longer survival.
The discovery of the genetic causes of familial (inherited) medullary thyroid cancer now makes it possible to identify family members carrying the abnormal RET gene and to remove the thyroid to prevent cancer from developing there.
Understanding the abnormal genes that cause sporadic (not inherited) thyroid cancer has led to better treatments as well. In fact, treatments that target some of these gene changes are already being used, and more are being developed (see below).
Most thyroid cancers can be treated successfully. But advanced cancers can be hard to treat, especially if they do not respond to radioactive iodine (RAI) therapy. Doctors and researchers are looking for new ways to treat thyroid cancer that are more effective and lead to fewer side effects.
Surgery is an effective treatment for most thyroid cancers, and it can usually be done without causing major side effects, especially when done by experienced surgeons.
Some people who have thyroid surgery are bothered by the scar it leaves on the neck. Newer approaches to surgery may help with this. For example, in endoscopic surgery, the surgeon operates on the thyroid by inserting, long, thin instruments through small incisions in the neck instead of making one larger incision.
In an even newer approach, the surgeon sits at a control panel and maneuvers robotic arms to do the surgery through an incision under the arm, so there is no scar in the neck. These approaches are much more likely to be used for thyroid conditions other than cancer at this time, but some doctors are now looking to see if they can be used for thyroid cancers as well.
Radioactive iodine (RAI) therapy
Doctors are looking for better ways to see which cancers are likely to come back after surgery. Patients with these cancers may be helped by getting RAI therapy after surgery. Recent studies have shown that patients with very low thyroglobulin levels 3 months after surgery have a very low risk of recurrence even without RAI. More research in this area is still needed.
Researchers are also looking for ways to make RAI effective against more thyroid cancers. For example, in some thyroid cancers, the cells have changes in the BRAF gene, which may make them less likely to respond to RAI therapy. Researchers are studying whether new drugs that target the BRAF pathway can be used to make thyroid cancer cells more likely to take up radioactive iodine. These types of drugs might be useful for people who have advanced cancer that is no longer responding to RAI therapy.
In general, thyroid cancers do not respond well to chemotherapy. But exciting data are emerging about some newer targeted drugs. Unlike standard chemotherapy drugs, which work by attacking rapidly growing cells (including cancer cells), these drugs attack specific targets on cancer cells. Targeted drugs may work in some cases when standard chemotherapy drugs do not, and they often have different (and less severe) side effects.
Tyrosine kinase inhibitors: A class of targeted drugs known as tyrosine kinase inhibitors (TKIs) may help treat thyroid cancer cells with mutations in certain genes, such as BRAF and RET/PTC. Many of these drugs also affect tumor blood vessel growth (see below).
In many papillary thyroid cancers, the cells have changes in the BRAF gene, which helps them grow. Drugs that target cells with BRAF gene changes, such as vemurafenib (Zelboraf®), dabrafenib, and selumetinib, are now being studied in thyroid cancers with this gene change.
In one study, giving selumetinib to patients with thyroid cancers that had stopped responding to radioactive iodine (RAI) treatment helped make some patients’ tumors respond to treatment with RAI again. It helped patients not only with BRAF muations, but also with mutations in a different gene called NRAS.
Other TKIs that have shown early promise against thyroid cancer in clinical trials include sorafenib (Nexavar®), sunitinib (Sutent®), pazopanib (Votrient®), cabozantinib (Cometriq), motesanib (AMG 706), axitinib (Inlyta®), and vandetanib (Caprelsa®).
Vandetanib and cabozantinib are both targeted drugs shown to be helpful in the treatment of medullary thyroid cancer (MTC) in clinical trials, and are now approved for use against advanced forms of the disease. Some other TKIs, such as sunitinib, sorafenib, and pazopanib, are already approved to treat other types of cancer, and might be useful against MTC and differentiated thyroid cancers if other treatments are no longer working.
Anti-angiogenesis drugs: As tumors grow, they need a larger blood supply to get enough nutrients. They get it by causing new blood vessels to form (a process called angiogenesis). Anti-angiogenesis drugs work by disrupting these new blood vessels. Some of the TKIs listed above, such as axitinib, motesanib, sunitinib, sorafenib, pazopanib, and cabozantinib, have anti-angiogenic properties.
Other targeted drugs: A recent early study found the combination of the chemotherapy drug paclitaxel (Taxol) with the targeted drug efatutazone could be helpful in patients with anaplastic thyroid cancer. Efatutazone targets a receptor called PPAR-gamma.
Last Medical Review: 02/24/2014
Last Revised: 03/20/2014