COACH - Comparing Two Different Methods to Suppress Thyrotropin in Patients With Advanced Thyroid Cancer

Most thyroid cancers can be cured with surgery, sometimes with radioactive iodine therapy. However, some patients have cancer that has spread, and some have cancer that comes back after treatment. For those with remaining cancer, lowering TSH levels is recommended. This is because thyroid cancer growth can depend on TSH, so reducing TSH can lower the risk of cancer returning and slow its growth in patients with cancer that can't be surgically removed. International guidelines recommend keeping TSH levels as low as \<0.1 mU/L for patients with advanced thyroid cancer. This advice is based on past studies, but it hasn't been tested in a controlled way. One old study suggested that not lowering TSH enough could lead to more cancer relapses. Another study suggested that lowering TSH more could help prevent cancer from getting worse in high-risk patients. However, a recent study found no link between TSH levels and better outcomes, and the researchers suggested doing a new study to confirm if this practice is truly beneficial. Lowering TSH levels to \<0.1 mU/L using levothyroxine has been the standard of care for treating advanced thyroid cancer for a long time. The researchers would like to investigate whether using levothyroxine to keep TSH levels between 0.1 and 0.5 mU/L is just as safe and effective for cancer treatment as the current recommendation of keeping it below 0.1 mU/L. The researchers also believe this study can help set TSH suppression targets based on cancer type, reducing unnecessary side effects from too much TSH suppression while still achieving the same cancer treatment results. If the researchers can prove that keeping TSH levels between 0.1 and 0.5 mU/L is just as safe and effective as the standard of care practice, we can change our standard treatment approach. This would help reduce symptoms for our patients.