Frank P. DawryFrank P. Dawry

Thyroid CancerThyroid Cancer TherapyTherapy Radioactive Iodine (I-131)Radioactive Iodine (I-131)

Types of Thyroid CancerTypes of Thyroid Cancer

Papillary or Papillary-FollicularPapillary or Papillary-Follicular Most common type; Most common type; Slow growingSlow growing Single encapsulated tumorSingle encapsulated tumor Spreads to regional lymph nodes, Spreads to regional lymph nodes,

later lung and bone.later lung and bone. FollicularFollicular

Less commonLess common More aggressiveMore aggressive Metastasizes via the blood streamMetastasizes via the blood stream

Hurthle Cell Tumor – similar to Hurthle Cell Tumor – similar to follicular but does not concentrate I-follicular but does not concentrate I-131131

MedullaryMedullary Originates in the parafollicular C-cellsOriginates in the parafollicular C-cells Little or no I-131 concentration Little or no I-131 concentration

AnaplasticAnaplastic Dedifferentiated papillary or follicular Dedifferentiated papillary or follicular

cancercancer Locally invasive with regional spread Locally invasive with regional spread

and early distant metastasesand early distant metastases Little or no I-131 concentrationLittle or no I-131 concentration

About 75% of Thyroid About 75% of Thyroid Cancers are Papillary and Cancers are Papillary and Papillary/follicular Papillary/follicular

About 15% are Follicular and About 15% are Follicular and Hurthle cell Hurthle cell

About 7% are Medullary About 7% are Medullary About 3% are AnaplasticAbout 3% are Anaplastic

Imaging findingsImaging findings

~10% of nodules are hot nodules

Thyroid Nodules WorkupThyroid Nodules Workupone approachone approach

<1cm

6mFollow-up

>1cm

Fine Needle Biopsy

Benign Papillary CaFollicular Lesion

Surgery

Post Surgical AblationPost Surgical Ablation

Performed to eliminate competition for I-131 by malignant cells throughout the body

Beta Particle TherapyBeta Particle Therapy

Benefit of RAI ablationBenefit of RAI ablationThyroglobulin (Tg) Can Be Used As A Tumor

Marker After A Successful Ablation>10 ng/ml = elevated above normal

Post Ablation ImagingPost Ablation Imaging7-10 days following ablation dose7-10 days following ablation dose

Too much tissue!

RAI AblationRAI Ablation laboratory workuplaboratory workup

TSHTSH Thyroglobulin (Tg) baselineThyroglobulin (Tg) baseline CBCCBC Serum BUN/creatinineSerum BUN/creatinine UrinalysisUrinalysis Serum calciumSerum calcium BETA HCG (serum pregnancy test - in women of BETA HCG (serum pregnancy test - in women of

child bearing age)child bearing age) Chest X-ray (to screen for pulmonary mets)Chest X-ray (to screen for pulmonary mets)

RAI AblationRAI Ablation Patient preparationPatient preparation

Near total thyroidectomyNear total thyroidectomy Discontinue Thyroxine (T4) 6 weeks prior Discontinue Thyroxine (T4) 6 weeks prior

to treatment to cause an increase in to treatment to cause an increase in TSH TSH

(goal >30-50 uIU/ml)(goal >30-50 uIU/ml)

T3 substituted for the first 3-4 weeks and T3 substituted for the first 3-4 weeks and then discontinue for 12-14 daysthen discontinue for 12-14 days

Low iodine diet for 7-10 daysLow iodine diet for 7-10 days

Treatment GuidelinesTreatment Guidelines Ablation Ablation

30 to 75 millicuries I-131 or more.30 to 75 millicuries I-131 or more. <30 millicuries traditionally used to avoid <30 millicuries traditionally used to avoid

patient being admittedpatient being admitted 30,000 rad to the remnant30,000 rad to the remnant

Requires individual dosimetryRequires individual dosimetry

MetastasesMetastasesTreatment Guidelines Treatment Guidelines

Empirical Empirical Beierwaltes protocol -Beierwaltes protocol -

Local metastasesLocal metastases 75 to 150 millicuries75 to 150 millicuries

Distal metastasesDistal metastases 150 to 300 millicuries150 to 300 millicuries

Dosimetric Dosimetric Benua -Benua -

Blood samples, and whole-body counts to determine retention and Blood samples, and whole-body counts to determine retention and clearance rates to determine the maximum safe doseclearance rates to determine the maximum safe dose

Delivers no more than 2 Gy (200 rad) to the whole bloodDelivers no more than 2 Gy (200 rad) to the whole blood Whole-body 48 hour retention rate < 120 millicuries (4440 MBq)Whole-body 48 hour retention rate < 120 millicuries (4440 MBq) <80 millicuries (2960) with pulmonary metastases<80 millicuries (2960) with pulmonary metastases

MaxonMaxon Thyroid remnant – 8,000 rad to nodal metastasesThyroid remnant – 8,000 rad to nodal metastases

DosimetryDosimetryDƩ = Dβ + DγDƩ = Dβ + Dγ

PET-probe Guided SurgeryPET-probe Guided SurgeryUseful in finding Iodine negative Useful in finding Iodine negative carcinomacarcinoma

Patient release >33 Patient release >33 millicuries administeredmillicuries administered

1. Will the administered activity of 131I exceed 33 mCi? No The patient may be treated as an outpatient. Ensure that written and oral patient

instructions are provided, and a written directive completed. Yes The patient may require hospitalization for treatment. Continue to Item 2. 2. Determine if the following criteria apply: Yes No The patient will maintain a prudent distance from others for at least the first 2

days. The patient will sleep alone in a room for at least the first night. The patient will not travel by airplane or mass transportation for at least the first

day. The patient will not travel on a prolonged automobile trip with others for at least

the first 2 days. The patient will have sole use of a bathroom for at least the first 2 days. The patient will drink plenty of fluids for at least the first 2 days.

The maximum likely dose to an individual exposed to the The maximum likely dose to an individual exposed to the patient [D (mrem)] must be less than 500 millirem – if not, patient [D (mrem)] must be less than 500 millirem – if not,

patient must be hospitalized until less than 30 millicuries or patient must be hospitalized until less than 30 millicuries or exposure rate at 1 meter is <5 mR/hourexposure rate at 1 meter is <5 mR/hour

Patient release >33 Patient release >33 millicuries administeredmillicuries administered

For Na131I treatment of a patient post-thyroidectomy for thyroid cancer:

D (mrem) = 2.27 Qo = ________ mrem, where D (mrem) is the maximum likely dose to an individual exposed to the patient and Qo is the

administered activity in millicuries (e.g., if you administer 100 mCi to the patient, then D (mrem) = 2.27 * 100 = 227 mrem).

For Na131I treatment of hyperthyroidism: D (mrem) = 8.84 Qo = ________ mrem,

where D (mrem) is the maximum likely dose to an individual exposed to the patient and Qo is the administered activity in millicuries.

Note: the above 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 specific patient, you must use Equation B-5 of the Regulatory Guide. You must write the entire equation below: D (mrem) =

BioassayBioassay

Florida State Regulation: 64E-5.625 Safety Instruction Florida State Regulation: 64E-5.625 Safety Instruction and Precautions for Radiopharmaceutical Therapy, and Precautions for Radiopharmaceutical Therapy, Brachytherapy, and Teletherapy.Brachytherapy, and Teletherapy. measure the thyroid burden of each individual who helped measure the thyroid burden of each individual who helped

prepare or administer a dosage of prepare or administer a dosage of liquidliquid iodine 131 within 3 iodine 131 within 3 days after administering the dosage.days after administering the dosage.

Nuclear Regulatory Commission, Part 35Nuclear Regulatory Commission, Part 35 requires that, for staff who helped prepare or administer a requires that, for staff who helped prepare or administer a

dosage of 131I to patients who were hospitalized for dosage of 131I to patients who were hospitalized for compliance with the patient-release criteria, a measurement compliance with the patient-release criteria, a measurement of thyroid burden must be made within three days of such of thyroid burden must be made within three days of such administration.administration.