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Thyroid Cancer Therapy

Thyroid Cancer Therapy. Radioactive Iodine (I-131). Papillary or Papillary-Follicular Most common type; Slow growing Single encapsulated tumor Spreads to regional lymph nodes, later lung and bone. Follicular Less common More aggressive Metastasizes via the blood stream

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Thyroid Cancer Therapy

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  1. Thyroid CancerTherapy Radioactive Iodine (I-131) Frank P. Dawry

  2. Papillary or Papillary-Follicular Most common type; Slow growing Single encapsulated tumor Spreads to regional lymph nodes, later lung and bone. Follicular Less common More aggressive Metastasizes via the blood stream Hurthle Cell Tumor – similar to follicular but does not concentrate I-131 Medullary Originates in the parafollicular C-cells Little or no I-131 concentration Anaplastic Dedifferentiated papillary or follicular cancer Locally invasive with regional spread and early distant metastases Little or no I-131 concentration About 75% of Thyroid Cancers are Papillary and Papillary/follicular About 15% are Follicular and Hurthle cell About 7% are Medullary About 3% are Anaplastic Types of Thyroid Cancer

  3. Imaging findings ~10% of nodules are hot nodules

  4. Thyroid Nodules Workupone approach <1cm >1cm Fine Needle Biopsy 6m Follow-up Papillary Ca Follicular Lesion Benign Surgery

  5. Post Surgical Ablation Performed to eliminate competition for I-131 by malignant cells throughout the body

  6. Beta Particle Therapy

  7. Benefit of RAI ablation Thyroglobulin (Tg) Can Be Used As A Tumor Marker After A Successful Ablation >10 ng/ml = elevated above normal

  8. Post Ablation Imaging7-10 days following ablation dose Too much tissue!

  9. RAI Ablationlaboratory workup • TSH • Thyroglobulin (Tg) baseline • CBC • Serum BUN/creatinine • Urinalysis • Serum calcium • BETA HCG (serum pregnancy test - in women of child bearing age) • Chest X-ray (to screen for pulmonary mets)

  10. RAI AblationPatient preparation • Near total thyroidectomy • Discontinue Thyroxine (T4) 6 weeks prior to treatment to cause an increase in TSH • (goal >30-50 uIU/ml) • T3 substituted for the first 3-4 weeks and then discontinue for 12-14 days • Low iodine diet for 7-10 days

  11. Treatment Guidelines Ablation • 30 to 75 millicuries I-131 or more. • <30 millicuries traditionally used to avoid patient being admitted • 30,000 rad to the remnant • Requires individual dosimetry

  12. MetastasesTreatment Guidelines Empirical • Beierwaltes protocol - • Local metastases • 75 to 150 millicuries • Distal metastases • 150 to 300 millicuries Dosimetric • Benua - • Blood samples, and whole-body counts to determine retention and clearance rates to determine the maximum safe dose • Delivers no more than 2 Gy (200 rad) to the whole blood • Whole-body 48 hour retention rate < 120 millicuries (4440 MBq) • <80 millicuries (2960) with pulmonary metastases • Maxon • Thyroid remnant – 8,000 rad to nodal metastases

  13. DosimetryDƩ = Dβ + Dγ

  14. PET-probe Guided SurgeryUseful in finding Iodine negative carcinoma

  15. Patient release >33 millicuries administered The maximum likely dose to an individual exposed to the patient [D (mrem)] must be less than 500 millirem – if not, patient must be hospitalized until less than 30 millicuries or exposure rate at 1 meter is <5 mR/hour

  16. 131 For Na I treatment of a patient post - thyroidectomy for thyroid cancer : D (mrem) = 2.27 Q = ________ mrem, o where D (mrem) is the maximum li kely dose to an individual exposed to the patient and Q is the o administered activity in millicuries (e.g., if you administer 100 mCi to the patient, then D (mrem) = 2.27 100 = 227 mrem). * 131 For Na I treatment of hyperthyroidism: D (mrem) = 8.84 Q = ________ mrem, o where D (mrem) is the maximum likely dose to an individual exposed to the patient and Q is the o administered activity in millicuries. Note: the abov e 2 calculations use occupancy factors discussed in Appendix B, section B.1.2 of NRC Regulatory Guide 8.39, and effective half - lives and uptake components found in Table B - 1 of NRC Regulatory Guide 8.39. If you use other values, as determined for your spec ific patient, you must use Equation B - 5 of the Regulatory Guide. You must write the entire equation below: D (mrem) = Patient release >33 millicuries administered

  17. Bioassay • Florida State Regulation: 64E-5.625 Safety Instruction and Precautions for Radiopharmaceutical Therapy, Brachytherapy, and Teletherapy. • measure the thyroid burden of each individual who helped prepare or administer a dosage of liquid iodine 131 within 3 days after administering the dosage. • Nuclear Regulatory Commission, Part 35 • requires that, for staff who helped prepare or administer a dosage of 131I to patients who were hospitalized for compliance with the patient-release criteria, a measurement of thyroid burden must be made within three days of such administration.

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