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2012 EDUCATIONAL BOOK - American Society of Clinical Oncology

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EVALUATION OF ADVANCED THYROID CANCER<br />

Sidebar 1. Treatment Considerations for Recurrent or Metastatic Differentiated Thyroid Carcinoma<br />

Consideration<br />

Surgery<br />

External-beam radiation<br />

Thyrotropin suppression<br />

Confirmation <strong>of</strong> optimal<br />

preparation for prior<br />

radioactive iodine<br />

treatments<br />

Bone lesions<br />

sary to adequately suppress TSH in patients with thyroid<br />

cancer. 12<br />

It is essential that the medical oncologist seeing patients<br />

with recurrent or metastatic DTC be familiar with issues<br />

usually addressed by endocrinologists or nuclear medicine<br />

physicians. For example, before considering treatment with<br />

either cytotoxic chemotherapy or molecularly targeted systemic<br />

agents, the medical oncologist should determine<br />

whether RAI is an option for the patient. There is no<br />

universally accepted definition <strong>of</strong> RAI-refractory DTC (Sidebar<br />

2). Some clinicians accept a rise in thyroglobulin level<br />

following administration <strong>of</strong> RAI as evidence <strong>of</strong> refractory<br />

KEY POINTS<br />

● Spectrum <strong>of</strong> thyroid follicular-cell derived cancers<br />

ranges from indolent differentiated thyroid cancers<br />

(DTC) to very aggressive undifferentiated thyroid<br />

cancer commonly known as anaplastic thyroid cancer<br />

(ATC).<br />

● Medullary thyroid cancer (MTC) originates from<br />

parafollicular c-cells <strong>of</strong> thyroid and is one <strong>of</strong> the best<br />

characterized solid tumors.<br />

● Surgery plays critical role in management <strong>of</strong> all types<br />

<strong>of</strong> thyroid cancers while targeted systemic therapies<br />

with levo-thyroxine for thyroid stimulating hormonesuppression<br />

and radio-iodine are restricted to management<br />

<strong>of</strong> differentiated thyroid cancer.<br />

● Tyrosine kinase inhibitors are promising novel therapies<br />

for patients with DTC and MTC. Vandetanib<br />

was approved by the U.S. Food and Drug Administration<br />

in 2011 for treatment <strong>of</strong> progressive or symptomatic<br />

advanced MTC.<br />

● Despite multimodality treatment with surgery, radiation<br />

and cytotoxic chemotherapy, prognosis remains<br />

dismal with median survival <strong>of</strong> 6 months in patients<br />

with advanced ATC.<br />

Specific Issues<br />

Selected patients may benefit from repeated neck dissections or metastatectomies<br />

<strong>of</strong> limited disease.<br />

Often useful to control inoperable relapses in the neck and treatment <strong>of</strong> foci <strong>of</strong><br />

metastatic disease, especially central nervous system or bone lesions<br />

Target serum thyroid stimulating hormone level �0.1 mU/L. May require 2.5<br />

mcg/kg/d or more <strong>of</strong> levothyroxine<br />

Was a low iodine diet maintained?<br />

Was the TSH adequately elevated via thyroid hormone withdrawal or recombinant<br />

TSH administration?<br />

Did the patient receive iodinated contrast medium in the 3 mos. preceding<br />

treatment with radioactive iodine?<br />

Was a low-iodine diet maintained prior to treatment with radioactive iodine?<br />

Bisphosphonates or RANK-ligand inhibitors reduce the risk <strong>of</strong> fracture.<br />

disease. Others cite lack <strong>of</strong> detectable radioactivity on a<br />

whole-body scan following diagnostic or therapeutic administration<br />

<strong>of</strong> RAI as definition <strong>of</strong> RAI-refractory disease.<br />

Although progression after RAI treatment as documented by<br />

conventional imaging with computerized tomography (CT),<br />

magnetic resonance imaging, or bone scans is probably the<br />

most conservative method <strong>of</strong> declaring a patient’s tumor to<br />

be RAI refractory, conventional imaging comparisons are<br />

<strong>of</strong>ten not available for patients who have been followed up<br />

exclusively by serum thyroglobulin levels and whole-body<br />

scans. Because <strong>of</strong> the inverse relationship between<br />

fluorodeoxyglucose-positron emission tomography (FDG-<br />

PET) avidity and RAI uptake, some clinicians consider a<br />

positive FDG-PET scan itself as a definition <strong>of</strong> RAIrefractory<br />

disease. 13,14<br />

Under certain circumstances, it is important to review<br />

how therapeutic RAI was administered to ensure that it was<br />

given in a setting in which efficacy was maximized. In order<br />

to facilitate maximal RAI uptake by the disease, there must<br />

not be a sink for the RAI. In general, normal thyroid tissue<br />

is more iodine avid than DTC; because <strong>of</strong> this, the presence<br />

Sidebar 2. Various Definitions <strong>of</strong> Radioactive Iodine<br />

(RAI) Refractory Differentiated Thyroid Carcinoma<br />

1. Lack <strong>of</strong> uptake seen on a whole-body scan following<br />

diagnostic RAI dosing<br />

2. Lack <strong>of</strong> uptake seen on a whole-body scan following<br />

therapeutic RAI dosing.<br />

3. Rising thyroglobulin following therapeutic RAI dosing<br />

4. Progression <strong>of</strong> lesions as documented by conventional<br />

imaging (e.g., computerized tomography,<br />

magnetic resonance imaging or bone scan) following<br />

therapeutic RAI dosing.<br />

5. Cumulative dose <strong>of</strong> � 600 mCi <strong>of</strong> 131-iodine ( 131 I)<br />

6. Fluorodeoxyglucose (FDG)–avid lesions on FDGpositron<br />

emission tomography.<br />

385

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