Indications, Ablation vs Adjuvant vs Definitive Radioactive Iodine treatment, Precautions and Side effects and Evidences

1. RADIOIODINE
TREATMENT IN DTC
Dr. Pradeep, MS MRCS
Mch Postgraduate in Surgical Oncology
Prof. M.P
. Viswanathan MS MCh
Prof. D. Suresh Kumar, MS DNB MCh DNB Unit
Tamil Nadu Govt Multi Superspecialty
Hospital, Chennai
12 Dec 2018

2. Objectives
■ Nuclear physics
■ Role in DTC
■ Preparation
■ Treatment Situations
■ Debates
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3. I 131
■ Neutron irradiation of Tellurium 130 or fission
product of Uranium 235
■ Biological half life 8.04 days
■ Radio decay – 90% beta radiation, 10% gamma
radiation
■ Hence poor resolution in Gamma cameras
■ Tissue penetration of 0.6 to 2 mm
■ I 123 – 84% gamma emission
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4. Radio Iodine Roles
Remnant Ablation
• Follow up with Post operative Tg and WBS
Adjuvant treatment
• Improve DFS in patients with high risk of recurrence
Therapeutic ablation
• Improve DFS and DSS by treating persistent disease
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5. Decision for RAI
■ Post operative disease status (ATA Risk
stratification)
■ Post operative serum Thyroglobulin
■ Radioactive Iodine diagnostic scan
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6. Thyroglobulin - Predictor
■ Thyroglobulin reach nadir by 3 to 4 weeks
postoperatively
■ TSH stimulated Tg < 1ng/mL - No evidence of
disease
■ When Thyroglobulin > 5-10ng/mL – increased
chance of identifying RAI avid metastases on post
ablation scan
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7. Post op Diagnostic Scan
■ Several studies mention Remnant ablation failure
if given in doses more than 3 mCi and delay in
therapeutic dose for more than 1 week.
■ When performed, pretherapy diagnostic scans
should utilize 123I (1.5–3 mCi) or a low activity of
131I (1–3 mCi), with the therapeutic activity
optimally administered within 72 hours of the
diagnostic activity
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8. Preablation WBS
Necessary??
JUSTIFICATION AGAINST
how much residual thyroid tissue
has been left
have little to no benefit
potential for stunning
presence of functioning metastases all the information one needs can be
obtained by other methods
whether pre-ablation preparation
is adequate
post-therapy scans are more sensitive
whether patient is surgically
ablated or not
patient inconvenience and costs are
too great
ensure the proposed high dose of
therapeutic 131I not irradiating a
physiological site such as the
breasts
treat these patients, anyway,
regardless of diagnostic WBS and/or
uptake values.
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9. 12/14/2018

10. ATA Recommendation
■ Useful when the extent of the thyroid remnant
or residual disease cannot be accurately
ascertained from the surgical report or neck
ultrasound
■ when the results may alter the decision to treat or
the activity of RAI that is to be administered.
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11. Limitations
■ Radioactive
■ Stunning effect
■ Penetration limited
■ Not useful in bone and bulky metastases
■ Possibility of RAI refractory disease
■ Poor differentiation
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12. Stunning
■ Radiobiological phenomenon.
■ Temporary suppression of iodine, trapping
function of the thyrocytes and thyroid cancer cells
as a result of the radiation given off by the
scanning (or first) dose of 131I
■ The frequency of stunning was 40%, 67%, and
89% after 3, 5, and 10 mCi respectively
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13. Stunning on Outcome of
ablation
■ Park et al. success rate of ablation after 131I scans
56% vs after 123I scans 72%
■ Muratet et al. Success rate of ablation after 3 mCi
is 50% vs after 1 mCi of 131I (76%, p < 0.001).
■ Even 1 mCi of 131I caused stunning in a few cases
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14. ATA Risk stratification
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15. ATA Risk stratification
2015
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16. 12/14/2018

17. 12/14/2018

18. Preparation
■ Thyroid Hormone withdrawal or Recombinant
human TSH (Thyrogen)
■ Goal TSH of >30mIU/L is necessary
■ Thyroxine withdrawn for 3 to 4 weeks, in case of
T3 withdrawal of 1 to 2 weeks is sufficient
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19. Thyrogen in
■ Comorbids that make iatrogenic hypothyroidism
risky
■ Pituitary disease
■ Delay in treatment of RAI may be deleterious
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20. Thyrogen
■ Two dose regimen
■ 0.9mg/mL
■ Now and 24 hours later
■ IM, buttock
■ Oral RAI can be given 24 hours after 2nd injection
■ Cost in India (4000 to 12000)
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21. 12/14/2018

22. Role of Low Iodine Diet
■ Spot Urinary Iodine estimation prior to RAI
■ Plujimen et al found a significantly higher ablation
rate in patients performing a 2-week LID
compared to the control group (65% vs. 48%)
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23. I 131
■ Oral liquid or capsule
■ Diagnostic – Outpatient basis
■ Ablation – Inpatient basis
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24. 12/14/2018

25. Remnant Ablation
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26. ■ No incremental benefit with RAI after undergoing Total or
near total thyroidectomy in PTMC.
■ No significant reduction in recurrence, or improved
disease specific survival or overall survival in 10 year
follow up.
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27. ■ The incremental benefit of RRA in low risk patients with
well-differentiated thyroid cancer after total or near-total
thyroidectomy who are receiving thyroid hormone
suppressive therapy remains unclear
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28. RAI on DSS or Overall
Survival
■ Not associated with improved DSS or Overall survival in
Very low risk and Low risk DTC patients
■ Obvious and significant benefit of RRA is noted in high
risk DTC patients
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29. Disease free status
■ No clinical evidence of tumor
■ No imaging evidence of tumor by RAI imaging (no uptake
outside the thyroid bed on the initial post treatment WBS
if performed, or if uptake outside the thyroid bed had been
present, no imaging evidence of tumor on a recent
diagnostic or post therapy WBS) and/or neck US
■ Low serum Tg levels during TSH suppression (Tg <0.2
ng/mL) or after stimulation (Tg <1 ng/mL) in the absence
of interfering antibodies
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30. Adjuvant therapy
■ Treat suspected microscopic residual disease in
absence of known distant metastases
■ Administered activities above those used for
remnant ablation up to 150mCi
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31. Post therapy WBS
■ Done 3 to 7 days after Ablative therapy
■ Can additionally detect distant metastases not seen in
Diagnostic WBS in 10 to 13% of patients
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32. Follow Up WBS
■ Low-risk and intermediate-risk patients (lower risk
features) with an undetectable Tg on thyroid hormone
with negative anti-Tg antibodies and a negative US
(excellent response to therapy) do not require routine
diagnostic WBS during follow-up.
■ Diagnostic WBS, either following thyroid hormone
withdrawal or rhTSH, 6–12 months after adjuvant RAI
therapy can be useful in the follow-up of patients with
high or intermediate risk (higher risk features) of
persistent disease and should be done with 123I or low
activity 131I.
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33. Pulmonary metastases
■ Micro metastases
– <2mm, not seen on anatomic imaging
– Rates of complete remission higher
– RAI is repeated every 6 months as long as
disease concentrates RAI
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34. Pulmonary metastases
■ Macro metastases
– RAI is preferred initially
– Risk of pulmonary fibrosis is higher
– Repeated only if there is reduction in size and
Thyroglobulin levels.
■ Further dose
– Disease response
– Age
– Any other metastases
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35. Bone metastases
■ RAI therapy of iodine-avid bone metastases has
been associated with improved survival and
should be employed, although RAI is rarely
curative.
■ The RAI activity administered can be given
empirically (100–200 mCi) or determined by
dosimetry.
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36. TENIS Syndrome
■ 10 to 15% of patients (Tg elevation, Negative IS)
■ Do CxR, Neck USG, CT or MRI, Bone scan
■ No evidence of structural disease after all this
■ Decision of Empirical RAI therapy
■ Based on PET/CT (must prior to it)
■ PET CT negative – proceed with Empirical RAI
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37. Tg cut off value
■ Not clear
■ 10ng/mL or more on Thyroid hormone withdrawl
■ 5ng/mL or more on Thyrogen
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38. Empirical RAI
■ Purpose
– Aid in disease location (in upto 50% of patients)
– As treatment for non surgical disease
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39. Dosimetry
■ Repeated sub therapeutic doses of I-131 might
induce dedifferentiation and a loss of tumor
iodine-concentrating ability.
■ Fixed dose method
■ Lesion based dosimetry
■ Maximal safe dose method
■ Useful in Renal insufficiency, Children, elderly,
Extensive pulmonary metastases
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40. Fixed Dose method
■ Depends on Disease extent
■ 100 – 175mCi for cervical nodal metastases
■ 150 – 200 mCi for Distant metastases
■ Maxon et al. patients with metastases that
persisted after I-131 therapy received
significantly lower radiation doses per millicurie
of administered I-131, suggesting need for
dosimetric approach
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41. Lesion based
■ I 131 dose
■ Co – Initial concentration of I 131 in lesion
■ T1/2 – effective half life activity inside that lesion
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42. Maximal safe dose
method
■ According to MSKCC, I-131 dose should not
■ exceed 2 Gy to blood
■ result in a body retention of 120 mCi at 48 h
■ result in lung retention of 80 mCi at 48 h in cases
of diffuse pulmonary metastasis
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43. Refractory to RAI
■ Malignant/metastatic tissue does not ever
concentrate RAI
■ Tumor tissue loses the ability to concentrate RAI
after previous evidence of RAI-avid disease
■ RAI is concentrated in some lesions but not in
others
■ Metastatic disease progresses despite significant
concentration of RAI.
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44. Side Effects
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45. Contraindications
ABSOLUTE RELATIVE
• Pregnancy and
Lactation
• High grade bone marrow
depression
• Breast feeding should
be stopped 2 months
before radioiodine
• Pulmonary fibrosis and poor
lung function in lung
metastases
• Considerable Xerostomia
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46. Safety Guidelines
■ Drink one cup of water every hour
■ Keep a distance of 3 feet from others
■ For first week, do not share anything with family
members
■ Sleep alone, flush toilet after usage
■ Not breastfeed
■ Not become pregnant for another 6 months to 1
year
■ No travel in flights for 3 months
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47. Summary
■ RAI not recommended for LOW RISK ATA patients
■ Considered for INTERMEDIATE RISK (specific
subgroups like nodal disease and elderly age)
■ Recommended in HIGH RISK patients
■ Preablation WBS is necessary in all patients
■ Thyrogen is non inferior to THW in preparation
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48. Summary
■ 30mCi of RRA is successful as 100 mCi
■ Macrometastases are not successfully treated
with RAI
■ No strong recommendation for Low Iodine diet
■ Empirical RAI in TENIS syndrome if PET CT is
negative
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49. References
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50. Thank You
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