Iodine 131 (131I) is an important treatment for differentiated thyroid cancer (DTC), and as the incidence of DTC increases, the concept of 131I treatment for this disease is constantly being updated. You may need to pay attention to these 34 points for the clinical management of DTC.
34 points of iodine 131 for differentiated thyroid cancer.
1. The main point in the evaluation of thyroid nodules is the differentiation between benign and malignant.
2. Emphasis should be placed on evaluating thyroid nodules with a family history of thyroid cancer, history of neck irradiation, age, gender, etc. associated with malignant features.
3. Serum thyroid stimulating hormone (TSH) levels should be routinely measured in patients with thyroid nodules.
4. Serum Tg (thyroglobulin) is not recommended to assess the benignity or malignancy of thyroid nodules.
5. Thyroid nodules >1 cm in diameter with higher than normal serum TSH should undergo thyroid 131I or 99Tc nuclear imaging to determine if the nodule has autonomic uptake.
CT, MRI and 18F-FDG PET are not recommended as routine methods to evaluate the benignity of thyroid nodules.
7. Fine needle aspiration biopsy (FNAB) has the highest sensitivity and specificity for preoperative evaluation of benign and malignant thyroid nodules.
8. Ultrasound-guided FNAB can improve the success rate and diagnostic accuracy of sampling.
9. Postoperative AJCC TNM staging and low, intermediate and high risk of recurrence stratification should be performed in all DTC patients to help predict patient prognosis and guide individualized postoperative treatment and follow-up programs.
10. After DTC surgery, selective application of 131I nail clearing therapy.
11. 131I nail cleansing therapy is contraindicated during pregnancy, lactation, or planned short-term (6 months) pregnancy.
12. Discontinue levothyroxine (L-T4) for at least 2 weeks or use thTSH to raise serum TSH to >30 mU/L prior to nail cleansing therapy.
13. A low iodine diet (< 50 ug/d) and avoid iodine-containing contrast agents and medications (e.g., amiodarone) should be used prior to 131I nail clearing therapy.
14. Provide radiation safety protection instruction to patients before 131I nail cleaning treatment.
15.The 131I dose of nail clearing treatment for non-high-risk DTC patients is 1,11-3,7 GBq.
A diagnostic nuclear scan (Rx-WBS) should be performed within 2 to 10 days after 131I nail clearing treatment.
17. Thyroxine therapy should be started within 24 to 72 h after 131I nail cleansing therapy in patients with DTC who have stopped taking thyroxine prior to treatment.
18. For iodine uptake DTC metastases or recurrent lesions, 131I nail cleansing therapy can be applied selectively.
19. For metastasis of lymph nodes in the neck, 131I 3,7~5,55 GBq should be given.
20. 131I is an effective treatment for DTC pulmonary metastasis. The common dose of 131I for DTC pulmonary metastasis is 5,55-7,4 GBq.
21. Surgical resection is recommended for isolated, symptomatic bone metastases.
Although 131I is difficult to cure bone metastases, it can improve the quality of survival of patients, so 131I therapy is recommended for bone metastases with iodine uptake.
23. Surgical treatment should be considered first regardless of whether the CNS metastases are iodine ingested or not.
24. All patients with DTC should be treated with TSH suppression after 131I therapy.
25. After 131I treatment, patients should be given appropriate TSH suppression therapy according to their risk stratification, with TSH suppression to <0.1 mU/L for medium- and high-risk DTC patients and 0.1-0.5 mU/L for low-risk DTC patients.
26. The starting dose of L-T4 varies depending on the patient’s age and concomitant disease.
27. L-T4 should be administered early in the morning on an empty stomach. During dose adjustment, serum TSH should be measured approximately every 4 weeks.
28. The dose of L-T4 should be increased appropriately during pregnancy according to the increase of gestational weeks and thyroid hormone and TSH levels should be measured regularly to adjust the dose of L-T4.
29. Pregnant patients with DTC who have received 131I therapy should maintain TSH suppression levels appropriate to their condition.
30. Care should be taken to prevent and treat the appropriate complications during suppression therapy.
31. Female DTC patients should avoid pregnancy for 6 to 12 months after 131I treatment. For males, contraception should be used for 6 months.
32. Establish a 131I treatment isolation area in accordance with radiation safety and medical safety to ensure radiation safety of patients and the surrounding environment.
MRI and 18F-FDCPET are not recommended for routine use in the follow-up of DTC.
34. In progressive iodine-refractory DTC where conventional treatment is not effective, treatment with targeted drugs such as sorafenib can be considered.