Radiotherapy
Radioactive Iodine (RAI) Therapy
- Preferred treatment for:
- Females planning pregnancy in the future
- Individuals with comorbidities increasing surgical risk
- Patients with previously operated or externally irradiated necks, or lack of access to an experienced surgeon
- Patients with contraindications to antithyroid agents or failed to achieve euthyroidism with antithyroid agents
- Also indicated for patients with congestive heart failure, periodic thyrotoxic hypokalemic paralysis, pulmonary hypertension or right heart failure
- Can be used as initial treatment or for relapses after trial of antithyroid agents
- 50-90% of patients become euthyroid within 3-12 months after treatment
- Usually takes 4-8 weeks to control symptoms
- Large goiter requires large dose to reduce risk of recurrence
- 5-50% of patients become hypothyroid after 1 year from treatment; 3-5% per year thereafter depending on the dose of radioactive Iodine
- Pretreatment with other agents
- Antithyroid agents: Usually unnecessary with mild-moderate disease, but necessary for severe disease (discontinue for at least 2-3 days prior to treatment and can be resumed 3-7 days after treatment)
- May be considered in patients at increased risk for complications due to worsening of thyrotoxicosis (ie patients with comorbidities and elderly patients)
- Beta-blocker may also be used prior to treatment to control symptoms especially in patients who are at increased risk for complications due to worsening of thyrotoxicosis (ie patients with comorbidities and elderly patients)
- Antithyroid agents: Usually unnecessary with mild-moderate disease, but necessary for severe disease (discontinue for at least 2-3 days prior to treatment and can be resumed 3-7 days after treatment)
- Posttreatment
- Antithyroid agents have radioprotective effect; therefore, administer after treatment only in poorly controlled hyperthyroidism
- Thyroid replacement should be carefully titrated as patient evolves from euthyroidism to hypothyroidism
- Contraindicated in pregnant women, breastfeeding
- Pregnancy should be deferred at least 6-7 months
- Pregnancy test should be done within 48 hours prior to treatment
- Contraindicated in patients with coexisting or suspected thyroid cancer and patients not able to comply with radiation safety guidelines
- Contraindicated in patients with moderate to severe or sight-threatening orbitopathy
- Can induce or worsen ophthalmopathy, particularly in smokers
- Consent form should be signed before initiating treatment