EANM Procedure Guideline For Therapy with Iodine-131

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1 EANM Procedure Guideline For Therapy with Iodine-131 I. PURPOSE The purpose of this guideline is to assist nuclear medicine practitioners in 1. evaluating patients who might be candidates for therapy with iodine-131 ( 131 I) for benign or malignant conditions 2. providing information for performing this treatment. 3. understanding and evaluating the sequelae of therapy. II. BACKGROUND A. Definitions 1. I-131 is a beta-emitting radionuclide with a physical half-life of 8.0 days, a principal gamma ray of 364 kev and a principal beta particle with a maximum energy of 0.61 MeV, an average energy of MeV and a range in tissue of 0.8 mm. 2. Therapy in this context means the oral administration of 131 I as sodium iodide. 3. Benign conditions in this context mean Graves disease (diffuse toxic goitre), toxic or non-toxic goitre, solitary hyperfunctioning toxic thyroid nodule or benign thyroid remnants from cancer surgery. 4. Malignant conditions include differentiated thyroid cancer that accumulates radioiodine or functioning thyroid cancer metastases.

2 B. Background Oral administration of 131 I Iodide has been used to treat benign and malignant conditions of the thyroid since the 1940 s. Physicians responsible for treating thyroid disease should have an understanding of the clinical pathophysiology and natural history of the disease processes, should be familiar with other forms of therapy and should be able to collaborate closely with other physicians involved in managing the patient. The treating physician should either see patients in consultation with the physician assuming overall management of the patient s condition or be prepared to assume that role. The physician should be appropriately trained and experienced in the safe use and administration of 131 I therapy. Clinicians undertaking unsealed source therapy must be knowledgeable about and compliant with all applicable national and local legislation and regulations. The facility in which treatment is administered must have appropriate personnel, radiation safety equipment, procedures available for waste handling and disposal, handling of contamination, monitoring personnel for accidental contamination and controlling contamination spread.

3 III. COMMON INDICATIONS A. Benign disease 1. Hyperthyroidism 131 I may be indicated as the initial or secondary treatment of Graves disease, toxic multinodular goitre or solitary toxic thyroid nodule. Avidity of the thyroid gland for iodide must be sufficient to permit accumulation of an adequate radiation dose. 2. Non-toxic multinodular/diffuse goitre 131 I therapy has been used successfully to diminish the size of non-toxic multinodular/diffuse goitre. 3. Post operative ablation of benign thyroid remnant (s) after thyroidectomy. a. A minimum of four weeks should elapse between surgery and radioiodine therapy to allow endogenous levels of TSH to rise to ulu/ml. TSH may not rise to this level if a large volume of functioning thyroid tissue remains. b. Ability of the remnant to accumulate radioiodine may be demonstrated by uptake measurement or imaging B. MALIGNANT DISEASE

4 1. Therapy of residual cancer, local and distant metastases The presence of thyroid tissue should be documented, either by imaging or biopsy. A rising thyroglobin titre is a useful indicator of residual or recurrent thyroid cancer. CONTRAINDICATIONS 1. Absolute Pregnancy; breastfeeding 2. Relative Unmanageable urinary incontinence Uncontrolled hyperthyroidism Active thyroid orbitopathy IV. PROCEDURE A. Facility The facilities required will depend on national legislation for the emission of beta and gamma emitting radiopharmaceuticals. If in-patient therapy is required by national legislation, this should take place in an approved facility with appropriately shielded rooms and en-suite bathroom facilities. The administration of 131 I should be undertaken by appropriately trained medical staff with supporting scientific and nursing staff.

5 B. Patient preparation 1. All patients: a. Should have given a clinical history and undergone physical examination. Therapeutic alternatives should be reviewed. b. Should have undergone Laboratory Medicine testing appropriate to the condition with results available to and reviewed by the treating physician. c. Should receive written and verbal information about the procedure prior to receiving therapy. This information should include details of the procedure, potential complications, side effects, alternatives, and expected outcome. Written informed consent should be obtained. d. Should be instructed on how to reduce unnecessary radiation exposure to family members and members of the public. Written instructions should be provided. e. Iodide-containing preparations, iodine supplements, thyroid hormones and other medications that potentially affect the ability of thyroid tissue to accumulate iodide must be discontinued for a sufficient time prior to 131 I administration. (See table).

6 f. Must not have received iodine-containing radiographic contrast for at least three to four weeks prior to planned 131 I therapy. In patients who have received large contrast loads or who have renal dysfunction, more time may be required. (See table). DRUG INTERACTIONS Type of medication Recommended time of withdrawal Antithyroid medication (e.g. 3-7 days propylthiouracil carbimazole) Natural or synthetic thyroid hormone ( e.g. thyroxine, tri-iodothyronine) 2 weeks for tri-iodothyronine 4 weeks for thyroxine Expectorants, vitamins, health food preparations, 1-2 weeks, depending on iodide content Sodium iodide Iodine containing medications (e.g. Variable, 1-6 months amiodarone) Topical iodine (e.g. surgical skin 1-2 weeks preparation) Radiographic contrast agents Intravenous or intrathecal ( water soluble) Oral fat soluble ( e.g. cholecystography) Oil based ( e.g. bronchography) Myelographic ( oil based) 3-4 weeks 3 months 6-12 months 2-10 years Table adapted in part from: Monograph: 131-I (iodide), European Association of Nuclear Medicine

7 2. For outpatients a. Regulations governing the maximum burden of 131 I and maximum dose rate at which a patient may be released vary according to national legislation. b. For patients with thyrotoxicosis, recent measurements of thyroid hormone levels (T3 and/or T4) and thyroid stimulating hormone (TSH) should be available. For patients with thyrotoxicosis, avidity of the thyroid gland for iodide must be established. This can be achieved quantitatively by radioiodine uptake measurements or qualitatively by thyroid scintigraphy. These procedures will exclude silent thyroiditis or factitious thyrotoxicosis. If neck uptake is not seen, a pelvic image may exclude struma ovarii. Interfering drugs or antithyroid medication should be withdrawn prior to uptake measurements as outlined above. c. For patients with malignant conditions, thyroid hormone medication must be withheld for a time sufficient to permit an adequate rise in TSH. This is at least ten days for triiodothyronine (T3) and four weeks for thyroxine (T4). Patients with a large burden of residual functioning thyroid tissue may not have the desired rise in serum TSH. Recombinant TSH may be used to

8 prepare patients for post surgical diagnostic studies. Its role in preparing patients for high activity 131 I therapy is not established. 3. For inpatients a. All patients i. Should be informed of the radiation precautions required. ii. Any significant medical conditions should be noted and contingency plans made in case radiation precautions must be breached for a medical emergency. iii. Nursing personnel must be instructed on radiation safety. iv. Nursing personnel may be provided appropriate radiation monitors (film badge, pencil dosimeters, etc.). v. Concern about radiation should not interfere with the prompt, appropriate medical treatment of the patient, should an acute medical problem develop.

9 b. Patients undergoing ablation of thyroid remnant i. Should be on a low iodide diet for about one week prior to administration of 131 I therapy. Dietary Sources of Iodide Iodized salt Milk/dairy products Eggs Marine seafood Seaweed and kelp products Bread made with iodide conditioners Celery Iodide containing multivitamins ii. At least four weeks should have elapsed between surgery and thyroid ablation. iii. Imaging is essential to confirm the ability of the tissue to take up 131 I prior to treatment c. Patients undergoing post-ablation therapy for residual, recurrent or metastatic disease.

10 i. Should be on a low iodide diet for about a week prior to administration of therapy. ii. Thyroid hormone medications must be withheld for a time sufficient to permit an adequate rise in TSH. This is at least ten days for triiodothyronine (T3) and four weeks for thyroxine (T4). Patients with a large burden of residual functioning thyroid tissue may not have the desired rise in serum TSH. Recombinant TSH may be used to prepare patients for diagnostic studies in the post-surgical setting. Serum TSH levels should ideally be greater than 30 ulu/ml. iii. A running total of administered activity of 131 I should be kept in the patient s record. iv. Imaging is essential to confirm the ability of tissue to take up 131 I prior to treatment. Measurement of serum thyroglobin level is also useful. C. Information pertinent to performing the procedure 1. For all patients

11 a. Female patients who have a potential to bear children should routinely be tested for pregnancy within a few days before the administration of the 131 I treatment. Occasionally, for social reasons (e.g., women who have taken the vows of celibacy) a pregnancy test may be omitted. b. All potentially breast feeding/lactating women should be asked if they are breast feeding/lactating. If so, breast-feeding should stop and therapy delayed until lactation ceases in order to minimize the radiation dose to the breast. The patient may not resume breast-feeding for that child. Breast-feeding may resume with the birth of another child. c. Assurance that the patient is continent of urine or that arrangements are made to prevent contamination caused by incontinence. 2. For patients with thyrotoxicosis a. Prior therapy and results with previous radioiodine (including amount administered), thionamides or surgery should be documented.

12 b. Results of recent 24-hour RAIU or qualitative evidence of iodide avidity of the thyroid. c. Estimated weight of gland based upon imaging or palpation if calculation of administered activity is to be performed. d. The presence or absence of nodules in the thyroid and their degree of function should be noted. e. Concomitant medications. 3. For patients with malignancy a. Histologic diagnosis. b. Evidence of functioning residual benign or malignant thyroid tissue. c. Total lifetime 131 I administered activity may be useful. C. Precautions 1. For patients with thyrotoxicosis a. Recent thionamide therapy usually increases radioresistance by causing rapid turnover of thyroidal iodine and by other mechanisms. This may require a compensatory increase in administered activity.

13 b. Hyperthyroid crisis can be precipitated inpatients with large iodide avid multinodular glands who are given large administered activities. Such patients and patients who are elderly, who suffer from known heart disease or have a history of congestive heart failure may need to be pre-treated with betablockers and/ or started on thionamides a few days after their radiodine treatment. 2. For patients with malignant disease Treatment side effects may occur and are generally dose-related. These include nausea and vomiting, sialadenitis, xerostomia, neck swelling, and cytopenia. These are rare with administered activities below 7400 MBq (200 mci). Hydration of the patient with instructions urging frequent urination for up to two weeks and efforts to increase salivary flow may reduce radiation exposure to the bladder and salivary glands. Antiemetics may be helpful.

14 D. Radiopharmaceutical: I-131 E. Radiation Dosimetry in Adults Absorbed Dose Assuming No Thyroid Uptake (Athyrotic) ORGAN mgy/mbq Bladder wall Lower colon wall Kidneys Ovaries Testes Stomach ICRP 53 (page 253) Absorbed Dose, Assuming 55% Thyroid Uptake and 20 gram gland (Hyperthyroid) Organ mgy/mbq Thyroid 790 Bladder Wall Breast Upper colon wall Ovaries Testes ICRP 53 (page 278) based on a 20g gland Administered 131 I Activity MBq MBq Thyroid Uptake (%) Radiation Dose to the Red Marrow* mgy/mbq Adult * dose may vary depending on the whole body effective half-life of I-131 ICRP53 pages Child (10yrs)

15 1. Calculation of administered 131 I activity a. For thyrotoxicosis The main aim of treatment should be to prevent persisting or recurrent hyperthyroidism. Since the incidence and rate of appearance of hypothyroidism is directly related to the delivered thyroid radiation dose, the optimal dose calculation for treatment should be based on measurements that permit the delivery of a specified and planned radiation bdose to the thyroid. This requires measurement of thyroid uptake, gland size, and an estimate of thyroidal turnover rate (based upon several uptake measurements over a period of one week). Many medical centers find this method of calculating the administered activity too onerous since it requires that the patient return on several occasions. As an alternative, most medical centers assume a generic thyroidal turnover rate. Many strategies have been proposed. The approach used by each practice should suit the practice setting. i. Some attempt to deliver a specific amount of radiation to the thyroid gland on the basis of 131 I absorbed per gram of gland. This generally ranges from MBq/gm (60 80 uci/gm) up to MBq/gm ( uci/gm). As a general rule, smaller administered

16 activities are associated with higher rates of treatment failure and lower rates of post-treatment hypothyroidism. ii. Some practices routinely deliver fixed administered activity for all patients. This may involve a small fixed amount ( MBq or 2 3 mci), repeated as necessary, a large fixed amount ( MBq or mci), or a sliding scale, with the administered activity based upon the size of the gland and/or severity of thyrotoxicosis. iii. For patients with nodular hyperthyroidism and for patients receiving repeat therapy for prior treatment failure, larger administered activities are usually needed. b. For thyroid malignancy i. For patients undergoing ablation of thyroid remnant, administered activities in the range of MBq ( mci) are usually given. ii. For patients undergoing re-treatment for residual disease or local recurrence, somewhat larger administered activities

17 (in the range of 5550 MBq (150 mci) are often used. iii. For patients with distant metastases, administered activities of 7400 MBq (200 mci) or more may be used. Caution is recommended in patients with diffuse lung metastases in view of the potential risk of radiation fibrosis. c. Patients should have a whole body scan performed one to two weeks after treatment for staging purposes. F. Sources of error 1. For hyperthyroid patients Sources of inaccuracy may occur in the thyroid uptake, the estimated weight of the gland and in unpredictable variations in effective half-life or radiation sensitivity of the gland. 2. For thyroid cancer a. If administered activities of 74 MBq (2.0 mci) or more of 131 I were used for the whole body iodine scan, stunning of the thyroid remnant or residual disease could alter the effectiveness of therapy.

18 b. Some tumors may possess cells of different radiosensitivity, which could predispose to ultimate failure of therapy. V. ISSUES REQUIRING CLARIFICATION A. The role of recombinant TSH in treatment of patients still on thyroid suppression. B. The use of 131 I whole body imaging prior to 131 I therapy for thyroid cancer and whether stunning of the thyroid remnant occurs. C. The necessity of treating small (<1.5 cm.) papillary thyroid cancers with 131 i. D. Blind retreatment of 131 I scan negative, thyroglobulin positive patients. VI. CONCISE BIBLIOGRAPHY 1. Brill DR, Perez CA, at al. The American College of Radiology Standard for the Performance of Therapy with Unsealed Radionuclide Sources. American College of Radiology, Barrington SF, Kettle AG, et al. Radiation dose rates from patients receiving iodine-131 therapy for carcinoma of the thyroid. Eur J Nucl Med 23: (1996). Published erratum appears in Eur J Nucl Med 1997: 24: Sparks RB, Siegel JA. The need for better methods to determine release criteria for patients administered radioactive material. Health Phys 1998: 75:

19 4. MIRD Committee of Society of Nuclear Medicine. MIRD Dose Estimate Report No. 5. J Nucl Med 1975; 16: Stabin M, Stubbs J, Toohey R. Radiation Dose Estimates for Radiopharmaceuticals 30 April Radiation Dose Internal Information Center, Oak Ridge, TN. 6. Schlumberger MJ. Papillary and follicular thyroid carcinoma. NEJM 1998: 338: Lerch H, Schober O, Kuwar T, et al. Survival of differentiated thyroid carcinoma studied in 500 patients. J Clin Oncol 1997: 15: Mazzaferri EL, Robyn J. Post surgical management of differentiated thyroid carcinoma. Otolaryngologic Clin N Amer 1996: European Association of Nuclear Medicine. Monograph [131- I] Iodide International Committee on Radiation Protection (ICRP). Publication 53. Pergamon Press. New York (275-8). K. Zanzonico PB, Brill AB, Becker DV, et al. Radiation Dosimetry: Chapter 9 p in Principles of Nuclear Medicine 1995 Ed. Wagner HN. VI DISCLAIMER

20 The European Association of Nuclear Medicine has written and approved guidelines to promote the cost effective use of high quality nuclear medicine therapeutic procedures. These generic recommendations cannot be rigidly applied to all patients in all practice settings. The guidelines should not be deemed inclusive of all proper procedures or exclusive of other procedures reasonably directed to obtaining the same results. Advances in medicine occur at a rapid rate. The date of a guideline should always be considered in determining its current applicability. VII DESCRIPTION OF THE GUIDELINE DEVELOPMENT PROCESS The EANM Radionuclide Therapy Committee has been involved in the process of guideline development for undertaking radionuclide therapies since A multinational group of therapy experts developed a series of monographs on the radioncuclide therapy agents licensed for use throughout Europe. Subsequently a series of protocols was published on the Internet for use by members of the European Association of Nuclear Medicine. The monographs and protocols were achieved through a process of consensus taking note of the evidence available at the time of writing. The monographs and protocols have been in the public domain for four years and comments have been received from members of the nuclear medicine community. The guidelines have been developed using material within the monographs and protocols and have been formatted to harmonise with the Society of Nuclear Medicine Therapy Guidelines format. Last amended:

Austin Radiological Association Nuclear Medicine Procedure THERAPY FOR THYROID CANCER (I-131 as Sodium Iodide)

Austin Radiological Association Nuclear Medicine Procedure THERAPY FOR THYROID CANCER (I-131 as Sodium Iodide) Overview Indications I-131 therapy for Thyroid Cancer, of the papillo-follicular type, is