Background
Differentiated thyroid cancer (DTC) is usually highly treatable, but a subset of patients develops distant metastases, meaning the cancer has spread beyond the neck to organs such as the lungs or bones. When these metastases still take up radioactive iodine, radioiodine therapy (RAIT) can be an important treatment option. The goal of RAIT is to deliver targeted radiation to cancer cells that retain the ability to absorb iodine.
For RAIT to work well, cancer cells need to express more of the sodium-iodide symporter, the protein that helps pull iodine into thyroid cells. This can be stimulated in two main ways: recombinant human TSH (rhTSH), a medication that raises TSH without requiring the patient to become hypothyroid, or thyroid hormone withdrawal (THW), which involves stopping thyroid hormone replacement and allowing the body’s own TSH level to rise naturally. Both methods are used in practice, but their relative impact on long-term outcomes in metastatic, radioiodine-avid DTC has been less certain.
