I-131 for Thyroid Cancer

What is I-131 therapy for thyroid cancer?

Your body doesn’t make iodine, so your thyroid absorbs and stores what you need from your diet. We use radiotherapeutic iodine—the isotope 131 (I-131)—to kill cancer cells in your thyroid. We can also use I-131 to treat thyroid cancer that has spread elsewhere in your body.  

Why am I having I-131 therapy?

I-131 irradiates thyroid cancer with minimal effect on the healthy tissue in the rest of your body. We can treat you with I-131 alone or in combination with surgery. We tailor your dose and combination of treatments to the type and stage of your thyroid cancer diagnosis.

What type of technology does I-131 therapy use?

I-131 therapy makes use of your body’s way of absorbing iodine—through the thyroid. To enhance absorption, we may ask you to eat a low-iodine diet for a week or two before your treatment. Before you begin treatment, we may change your thyroid medications to increase your level of thyroid-stimulating hormone.

Changing your thyroid medication can change your hormone levels. You may temporarily experience:

  • Constipation
  • Distraction or difficulty concentrating
  • Muscle aches
  • Tiredness
  • Weight gain    

What conditions are treated using I-131 therapy?

We use I-131 to treat specific types of thyroid cancer, including papillary or follicular thyroid cancer. This therapy does not affect anaplastic and medullary thyroid carcinomas because they do not absorb iodine.

What will I experience during I-131 therapy?

We will give you a small capsule or liquid to swallow. Depending on the dose of therapy you receive, your body may give off radiation for a few days after treatment. You may have to remain in the hospital during that time. You will stay in a special isolation room that protects others from exposure. Your provider will discuss this with you in detail if needed.

Will I have side effects?

You may experience side effects that could include:

  • Dry eyes or excessive tearing
  • Dry mouth
  • Loss of taste or change of flavors
  • Nausea or vomiting
  • Reproductive organ changes, depending on the dose of radiation you receive 
  • Swelling and tenderness of the salivary glands
  • Tenderness in your neck 

Your provider will talk to you about the possible side effects and ways to manage them.