I. Iodine-131 treatment for Graves’ hyperthyroidism
Features.
(i) Simplicity: By taking sodium iodide solution orally once, iodine-131 is absorbed into the bloodstream through the gastrointestinal tract and taken up by the thyroid gland, which continuously emits β-rays to shrink the thyroid gland, resulting in a reduction of thyroid hormone synthesized by the thyroid gland and the disappearance of hyperthyroidism symptoms.
(ii) Safety: Since iodine-131 can be taken up by the thyroid gland with high specificity and the maximum range of beta rays emitted by iodine-131 is only 3.63mm, the therapeutic effect of beta rays on the thyroid gland is strong, while the effect on the tissues around the thyroid gland and other organs is extremely small.
Scholars at home and abroad have conducted follow-up studies on patients treated with iodine-131 for hyperthyroidism for more than half a century, and compared with the natural incidence of cancer in the general population, no increase in the incidence of leukemia, cancer, or malformation was seen, and the incidence of thyroid cancer was significantly lower than the natural incidence in the general population. Both theoretically and practically, it is proved that iodine-131 treatment for hyperthyroidism is an exceptionally safe treatment method.
(c) High cure rate: Through iodine uptake function examination of thyroid gland, accurate determination of thyroid gland size and individualized and optimal administration of treatment dose to patients according to their hyperthyroidism, the one-time cure rate is improved, with a few patients requiring 2 treatments and very few patients requiring 3-4 treatments.
(iv) Low relapse rate: Since the hyperfunctional and hyperplastic thyroid cells have been destroyed, it is not easy to relapse rate (its relapse rate is only 1-4%).
Indications.
1. Patients with Graves’ hyperthyroidism, allergy to antithyroid drugs, poor efficacy of antithyroid drugs, multiple relapses after antithyroid therapy drugs;
2.Recurrence after surgery;
3.Graves hyperthyroidism with leukocytopenia or thrombocytopenia;
4. Graves’ hyperthyroidism with atrial fibrillation.
Contraindications.
1, pregnancy, lactation;
2.Severe renal insufficiency;
3.Acute myocardial infarction.
II. Postoperative radioactive iodine-131 therapy for differentiated thyroid cancer
Thyroid cancer is the most common malignant tumor of the endocrine system, accounting for 1.1% of all malignant tumors (about 0.5% in men and 2.0% in women). The incidence of thyroid cancer is increasing year by year, and it is a growing concern. Currently, thyroid cancer is among the top 10 malignant tumors, and it is the eighth among female malignant tumors.
Differentiated thyroid cancer (DTC) is the most common type of thyroid cancer, accounting for about 90% of the cases, and is mainly composed of papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC). Follicular Thyroid Carcinoma (FTC) and, to a lesser extent, Hürthle cell carcinoma.
Most DTCs progress slowly and have a nearly benign course with a high 10-year survival rate, but certain histological subtypes (hypercellular, columnar cell, diffuse sclerosing, solid subtype of PTC and extensive invasive attack of FTC, etc.) are prone to extrathyroidal invasion, vascular invasion and distant metastasis, with a high recurrence rate and relatively poor prognosis. Iodine-131 therapy is a major step in the postoperative treatment of most DTCs and has become an important component of comprehensive DTC treatment.
Significance of iodine-131 therapy
Iodine-131 treatment for DTC consists of two levels: firstly, I-131 is used to remove residual thyroid tissue after DTC surgery (thyroid remnant ablation); secondly, I-131 is used to remove metastases of DTC that cannot be removed by surgery (subsequent further treatment of metastases). Subsequent further treatment of metastases is referred to as “clearing”. I-131 treatment after DTC surgery can achieve very good results, mainly to improve the prognosis, including delaying the time of recurrence, reducing the recurrence rate and reducing distant metastases.
I-131 treatment can significantly improve patients’ recurrence-free survival, progression-free survival and disease-free survival. It has also been documented that some patients with low-risk DTC do not benefit from nail-clearing therapy.
Indications for iodine-131 therapy
The ATA guidelines for nail clearance are: all patients with stages III and IV, all patients younger than 45 years of age and most patients older than 45 years of age with stage II, and selective stage I patients, especially those with multiple tumor lesions or lymph node metastases or with extrathyroidal or vascular infiltration and aggressive pathology. Indications for direct access to thyroid hormone suppression without 131I therapy should meet the following conditions: complete surgical excision of the lesion; non-invasive pathological type; no thyroid envelope invasion; single PTC less than 1 cm in diameter or FTC less than 2 cm in diameter without cervical lymph node metastasis.
Dose selection for DTC treated with iodine-131
The ideal dose of iodine-131 should be based on the absorbed dose, but at present it is difficult to calculate this accurately. Clear nail doses of 1.11-3.7 GBq (30-100 mCi) are generally given.
Recent multicenter clinical studies suggest that there is no significant difference in the efficacy of nail clearance in patients with non-high risk total thyroidectomy DTC using a nail clearance dose of 1.11 GBq versus 3.7 GBq. For patients with residual surgically unresected DTC tissue in the neck, inoperable lymph nodes or distant metastases in the neck, or patients who refuse surgery, or patients with unexplained elevated serum Tg levels after total thyroidectomy, nail clearing therapy should be combined with focal clearing therapy by directly administering 3.7-7.4 GBq (100-200 mCi).