Radioiodine Therapy in the Treatment of Thyroid Cancer

What is Radioiodine Therapy?

Radioiodine therapy, also known as iodine therapy or radioactive iodine treatment, is a medical treatment using radioactive iodine isotopes to treat certain conditions. It's particularly important in treating thyroid cancer and some thyroid diseases. There are mainly two types of radioactive iodine therapies:

• Iodine-131 therapy. This is the most common treatment, using the radioactive isotope iodine-131 to destroy thyroid cancer cells or reduce the size of a goiter.
• Iodine-123 therapy. Here, radioactive iodine is used for diagnostic purposes, such as thyroid scintigraphy, to assess thyroid function.

What are the indications for radioiodine therapy?

Radioiodine therapy has several indications, including:

• Thyroid cancer. Radioactive iodine therapy is used to treat differentiated thyroid cancer (papillary or follicular) after surgery.
• Goiter. Therapy can reduce the size of a goiter causing symptoms.
• Thyroid hyperfunction. Therapy can treat hyperthyroidism caused by diseases such as Graves' disease.

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How does radioiodine therapy work in the treatment of thyroid cancer?

Types of treatment

When treating thyroid cancer with radioiodine therapy, it's important to know that this iodine treatment can be used with several objectives. Indeed, in some patients with thyroid cancer, radioiodine therapy is used after surgery to destroy remaining cancer cells, while in others it can be useful in reducing the risk of recurrence. Furthermore, when cancer is detected at advanced stages, radioiodine therapy may have a palliative purpose to reduce symptoms and improve quality of life.

Treatment phases

Radioiodine therapy in the treatment of thyroid cancer is performed in several stages, here are the main ones:

• Preparation. The patient follows a low-iodine diet for 1 to 2 weeks to increase the absorption of radioactive iodine.
• The patient takes a capsule or solution containing the radioactive isotope I-131 orally.
• The radioactive iodine is absorbed by the thyroid gland and cancer cells.
• Radiation emission. Radioactive iodine-131 emits beta and gamma radiation that destroys cancer cells.

What are the consequences of radioiodine therapy in thyroid cancer?

Treatment of thyroid cancer with radioactive iodine (I-131) can have short-term and long-term consequences.

Short-term consequences (a few days/weeks)

The main short-term side effects are generally not dangerous, but can cause discomfort:

• Nausea and vomiting, common and usually temporary.
• Diarrhea caused by irradiation of the intestines.
• Sore throat due to inflammation of the thyroid gland.
• Temporary loss of appetite.
• Fatigue due to therapy and reduced thyroid activity.
• Temporary taste changes.
• Oral mucosa irritation.

Long-term consequences (months/years)

After receiving radioiodine therapy for thyroid cancer, some patients may experience side effects a few months or years later. These include:

• Hypopituitarism, including reduced pituitary function.
• Hypothyroidism, necessitating lifelong hormone therapy.
• Sexual dysfunction, rare and generally disappears over time.
• Rare infertility, especially in women.
• Tooth root damage.
• Cataracts in older people.
• Leukemia with a very low risk (less than 1%).
• Increased but low risk of other neoplasms.