Jiraporn Sriprapaporn, M.D. Nuclear Medicine Radiology Siriraj Hospital
RAI TREATMENT FORTHYROID DISORDERS HYPERTHYROIDISM Graves’ disease Toxic adenoma Multinodular toxic goiter (Plummer’s disease) THYROID CANCER DTC
Treatment of Hyperthyroidism Medical Surgical Radioactive iodine
Medical Treatment of HyperthyroidismTitrate the antithyroid drug dose every 4 weeksuntil thyroid functions normalize.Some patients with Graves disease go into aremission after treatment for 12-18 months, andthe drug can be discontinued.Notably, half of the patients who go intoremission have a recurrence of hyperthyroidismwithin the following year.Nodular forms of hyperthyroidism (toxic MNGand toxic adenoma) are permanent conditionsand will not go into remission. eMeddicine.com
Radioactive Iodine TherapyRadioactive iodine therapy is the mostcommon treatment for hyperthyroidism inadults in the United States.Although the effect is less rapid than it isin antithyroid medication orthyroidectomy, it is effective and safe anddoes not require hospitalization. eMeddicine.com
RAI Treatment for HyperthyroidismRAI is widely used for > 40-50 yrs. No evidence of increased risk to developmalignanciesI-131 solution Less expensive than I-131 capsule Easily to adjust the doseNo patient isolation is necessary butprecaution is likely.Need birth control for women in reproductivelife during the course of RAI treatment !!
RAI Treatment forHyperthyroidism:Indications Failed medical/surgical treatment-relapse Serious adverse effects of antithyroid drugs: drug allergy, agranulocytosis Inconvenience for frequent contact Poor compliance of medications Poor socioeconomic problems Presence of serious associated medical illness eg. heart failure
RAI Rx for Hyperthyroidism:Contraindications Pregnant LactatingPrecaution: Severe hyperthyroidism
I-131 Dose CalculationDose Determination - formula below Gland size, % uptake, dose of I-131 /gram thyroid tissueOther factors Severity of hyperthyroidism Types of hyperthyroidism: nodular* vs diffuse Other clinical parametersRAI Dose = [Thyroid mass (g) x 80-200 uCi/gm]/% uptake
RAI Rx: ProceduresStop antithyroid drugs for 5-7 days24 hr. I-131 uptakeI-131 Rx dose according to calculation.Combined medical Rx in severe thyrotoxic pts.Peak result of RAI Rx needs about 3-4 months.Long term F/U, monthly after 1st RAI Rx &reevaluate before reRx.Repeat RAI Rx: usually 3-6 mo interval if stillhyper.Thyroid H. replacement if permanenthypothyroidism is developed.
RAI Treatment for ThyroidCancer: Indications Differentiated thyroid carcinoma Papillary carcinoma* Mixed papillary-follicular carcinoma Follicular carcinoma (Hurthle’s cell carcinoma)*EXCEPT: Occult tumors <1 cm without invasive properties or metastatic evidence
RAI Treatment of Thyroid CancerSURGERY Near-total thyroidectomyRAI TREATMENTHORMONAL TREATMENT Suppressive dose of thyroid hormone (T4)LONG-TERM FOLLOW-UPCHEMOTHERAPY OR ERT#
Rai Treatment for DTC:ContraindicationsPregnancyBreast feedingAlso birth control for women in reproductive lifeduring the course of RAI treatment !!
RAI Treatment for DTCAblative treatment Thyroid remnant remaining postop. % uptake > 0.5% Dose 30-100mCiTreatment of recurrent or metastatictumors: Dose:150-200 mCi Functioning tumors that take up radioiodine Rising Tg but diagnostic dose could not reveal evidence of tumor*
Rationales of I-131 Ablation1. To destroy any residual microscopic disease.2. To increase specificity of subsequent 131I scanning for detection of recurrent or metastatic disease by elimination of uptake by residual normal tissue; and3. To improve the value of measurements of serum thyroglobulin as a serum marker derived only from malignant thyroid cells. Sherma SI Lancet 2003
Benefits of I-131 TherapyDecreases local recurrenceImproves survival in patients followinglocal recurrenceImprove patients’ conditions with bonemetastases Mazzaferri EL Am J Med 1994;418-28
RAI Treatment:Regulations If > 30 mCi : Patient isolation for a few days (usually 2-3 days) is necessary, ie. ADMISSION is required! If < 30 mCi : No isolation is required, thus OPD cases are OK! D/C when retained radioactivity < 30 mCi or dose rate < 5 mrem/hr
100 mCi I-131 TreatmentSeparate the patient for 40 hr Day Distance Time D1 1 ft 20 min D2 1 ft 1 hr D3 1m 10 hr
RAI Treatment for DTC:Techniques Patient preparation: withdraw T4 for 4-6 weeks, or T3 for 2 weeks before RAI Rx Low iodine-containing diet intake for 1 Wk On admission, prepare sour candies or fruits, etc Avoid radioactivity contamination to the body and the room Frequent voiding after Rx esp. in the first few days.
RAI Treatment for DTC:Complications Early complications Acute radiation sickness Acute sialoadenitis Radiation thyroiditis Pain, hemorrhage & swelling in the metastases Transient BM suppression Late complications Malignancies- leukemia 2% vs 0.1%
Follow-up of DTC Pts.Clinical history & physical examinationBlood Tests Serum thyroid hormones levels (TSH 0.1- 0.4 mIU/L) Tumor marker ie. Tg (N < 1 ng/ml) & TgAb (N < 25 mIU/L) Calcium balance, CBCI-131 TBS at 6 mo-1 yr post Rx until negative* (also other parameters are negative)Other investigations eg. CXR-yearly, Tl-201, Tc-99m MIBI scan, CT scan, MRIRepeat RAI Rx: at least 6-12 months interval