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Radiation Oncology Residency > Thyroid cancer > Flashcards

Thyroid cancer Flashcards

1
Q

Name the anatomic subdivisions/lobes of the thyroid

A

Subdivisions/lobes of the thyroid:

  1. Right lobe
  2. Left lobe
  3. Isthmus
  4. Pyramidal lobe (in 50% of individuals is remnant of thyroglossal duct)
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2
Q

In the thyroid follicle, what are the normal functions of the epithelial follicular cells and the parafollicular cells?

A 
Epithelial follicular cells: remove iodide from the blood and use it to form T3 and T4 thyroid hormones
Parafollicular cells (C cells): lie just outside of the follicle cells and produce calcitonin
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3
Q

What is the most common endocrine malignancy?

A

Thyroid cancer (TCa) is the most common endocrine malignancy, but is only 1% of all diagnosed malignancies.

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4
Q

What is the estimated incidence of new Thyroid Ca Dx and deaths in the United States?

A

There are an estimated 57,000 new Dx (3/4 women) and 2,000 deaths in 2017.

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5
Q

What are the 3 main TCa histologies in decreasing order of frequency?

A

Differentiated (follicular-derived) thyroid carcinoma (DTCa) (∼94%) > medullary (2%–4%) > anaplastic (2%)

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6
Q

What are the 3 subtypes of Differentiated thyroid Ca in decreasing order of frequency?

A

Papillary (90% of all TCa) > follicular > Hürthle cell carcinoma

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7
Q

What is happening to the incidence of diagnosed papillary TCa?

A

The incidence of papillary TCa is increasing (by ∼20% over the past 50 yrs, largely driven by better surveillance/detection of smaller lesions).

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8
Q

What is the typical age at Dx for follicular vs. papillary TCa?

A

Follicular incidence peaks at 40–60 yrs of age, whereas papillary peaks at 30–50 yrs of age.

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9
Q

Is there a sex predilection for papillary or follicular TCa?

A

Yes. Both papillary and follicular TCa more commonly affect females than males (3:1).

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10
Q

What is the strongest risk factor for papillary TCa?

A

RT exposure to the H&N as a child is the strongest risk factor for papillary TCa. There is no increased risk if exposure is after age 20 yrs. Most papillary
cases are sporadic.

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11
Q

Name 4 genetic disorders associated with papillary TCa

A

Genetic disorders associated with papillary TCa:

  1. Familial polyposis
  2. Gardner syndrome
  3. Turcot syndrome
  4. Familial papillary carcinoma
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12
Q

Name a genetic disorder associated with follicular TCa.

A

Cowden syndrome (PTEN gene mutation) is associated with follicular TCa.

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13
Q

Medullary TCa arises from what precursor cell?

A

Medullary TCa arises from the calcitonin-producing parafollicular C cells.

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14
Q

Name 2 genetic syndromes associated with medullary TCa.

A

MEN 2a and MEN 2b (RET gene mutation) are associated with medullary TCa.

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15
Q

What % of medullary TCa is related to a genetic syndrome?

A

∼25% of medullary TCa is related to a genetic syndrome.

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16
Q

Name the nerve that lies in the tracheoesophageal (TE) groove, post to the right/left thyroid lobes

A

The recurrent laryngeal nerve lies in the TE groove.

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17
Q

What are the primary, secondary, and tertiary lymphatic drainage regions of the thyroid?

A

Primary: central compartment (level VI or paralaryngeal and paratracheal), Delphian (prelaryngeal) LNs
Secondary: cervical, SCV, and upper mediastinal LNs (levels III–IV, VII)
Tertiary: upper cervical (level II)/retropharyngeal LNs

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18
Q

What % of palpable thyroid nodules are malignant?

A

Only 5% of palpable thyroid nodules are malignant

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19
Q

In a pt with low TSH and a nodule that shows uptake on I-123 or Tc-99 scan, what is the likely Dx?

A

Adenomas commonly present with low TSH and increased uptake on I-123 or Tc-99 scans.

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20
Q

Which TCa subtypes are difficult to distinguish from adenomas on FNA?

A

Follicular and Hürthle subtypes are difficult to distinguish from adenomas. Histologically, they show only follicular structures. Papillary TCa shows both papillary and follicular structures, which helps to distinguish it from
adenomas.

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21
Q

What pathologic criteria must be met to make the Dx of Hürthle cell TCa?

A

The Dx requires hypercellularity with >75% Hürthle cells (also referred to as oncocytic cells), which are characterized by abundant eosinophilic granular content.

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22
Q

Which TCa subtype is more likely to present with N+ Dz: papillary or follicular?

A

Papillary TCa (∼30% node+) is more likely to spread to LNs than follicular (∼10% node+).

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23
Q

Name the 2 major and 3 minor prognostic factors for DTCa.

A

Major: age and tumor size (<55 yo, ≤4 cm, respectively, have better prognosis)
Minor: histology, local tumor extension, LN status

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24
Q

What variables constitute the mnemonic AMES risk group system?

A

Age, Metastasis, Extent, Size

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25
Q

Which pts are low risk?

A

Young (<55 yo), no DMs

Older with minor tumor capsule involvement and tumor <4 cm and no DM

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26
Q

For TCa, what sizes distinguish AJCC 8th edition T1, T2, and T3 tumors?

A

T1: ≤2 cm (T1a if ≤1 cm; T1b if >1 cm)
T2: 2–4 cm (limited to thyroid)
T3: >4 cm (T3a if in thyroid; T3b if any size and extension into strap muscles only)

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27
Q

What is the difference b/t T4a and T4b TCa lesions?

A

T4a: gross extension but still technically resectable (invasion of larynx, trachea, esophagus, SQ tissues, recurrent laryngeal nerve)
T4b: unresectable Dz (invasion of prevertebral fascia/spine, carotid artery encasement, mediastinal vessels)

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28
Q

What is the difference b/t N1a and N1b in TCa?

A

N1a: mets to any level VI (pre-/paratracheal, prelaryngeal) or VII (cervical neck, upper mediastinal) LNs; unilat or bilat
N1b: mets to levels I–V, or retropharyngeal LNs

29
Q

List the latest AJCC 8th edition (2018) stage groupings for papillary and follicular TCa.

A

Stage I: M0 and age <55 yrs or T1–2N0M0 and age ≥55 yrs
Stage II: M1 and age < 55 yrs or T1–2N1, T3N(any) and age ≥55 yrs
Stage III: T4aN(any)M0 and age ≥55 yrs
Stage IVA: T4bN(any)M0 and age ≥55 yrs
Stage IVB: T(any)N(any)M1 and age ≥55 yrs

30
Q

What is unique about the staging of nonmedullary TCa?

A

It is age dependent; it differs for pts > or <55 yo.

31
Q

Can a pt <55 yo with follicular or papillary TCa have stage III or IV Dz?

A

No. A pt <55 yo with follicular or papillary TCa cannot have stage III or IV Dz.

32
Q

What is the stage of a 37-yo pt with Hurthle TCa and a solitary bone met?

A

Stage II. If the pt were 56 yo, he or she would be stage IVB.

33
Q

What is the stage of a 56-yo pt with an unresectable primary DTCa and no mets?

A

Stage IVA. If pt was 44 yo, he or she would be stage I.

34
Q

What must be done prior to an I-123 or I-131 scan?

A

TSH stimulation must be done prior to an iodine scan.

35
Q

What are 2 ways to do TSH stimulation?

A

TSH stimulation can be accomplished through thyroid hormone withdrawal or by using recombinant TSH.

36
Q

What are some advantages of recombinant TSH stimulation?

A

Fewer side effects and a shorter period of elevated TSH (theoretically, a lower risk of tumor progression)

37
Q

What are the approved indications for recombinant TSH stimulation?

A

Recombinant TSH is approved for f/u iodide scans and for the I-131 Tx of low-risk pts.

38
Q

What sites of the body show a physiologic uptake of iodide?

A

The salivary glands and the GI tract show physiologic uptake d/t the presence of iodide transporters.

39
Q

What is the 10-yr OS for papillary vs. follicular TCa?

A

Similar when matched for stage, 85%–95%

40
Q

Is the presentation and Tx of Hürthle cell carcinoma more similar to that of papillary or follicular TCa?

A

It is more similar to follicular TCa; however, Hürthle cell carcinoma has a slightly higher DM rate and worse prognosis (10-yr OS ∼70%–80%).

41
Q

Estimate the 10-yr OS for pts with localized vs. N+ medullary TCa

A

For localized medullary TCa, the 10-yr OS is ∼90%. If N+, the 10-yr OS is ∼70%.

42
Q

What are the stage groupings for anaplastic TCa?

A

All anaplastic TCa is stage IV. Stage IVA is T1–3aN0 (resectable), stage IVB is N1 or T3b–4 (unresectable), and stage IVC is metastatic.

43
Q

Estimate the MS and the 1-yr OS for pts with anaplastic TCa.

A

MS is ∼6 mos and the 1-yr OS is ∼20% for all pts with anaplastic TCa.

44
Q

Does the tall cell variant have a more favorable or unfavorable prognosis when compared to classic papillary TCa?

A

The tall cell variant has an unfavorable prognosis (10-yr OS ∼75%) when compared to classic papillary carcinomas.

45
Q

What is the most frequent site of DM in papillary and follicular TCa?

A

Lung (∼50%), f/b bone, CNS

46
Q

Generally, what is the Tx paradigm for TCa?

A

DTCa Tx paradigm: primary Sg (even in M1 Dz) → observation vs. adj Tx

47
Q

What are the 3 surgical options in TCa?

A

Surgical options in TCa are:

  1. Lobectomy + isthmusectomy
  2. Near-total thyroidectomy
  3. Total thyroidectomy
48
Q

What is the difference b/t near-total and total thyroidectomy?

A

Near-total is less aggressive around the recurrent laryngeal nerve.

49
Q

For which pts with papillary TCa is a lobectomy + isthmusectomy adequate?

A

Controversial. It is a good option for pts with none of the following risk factors: age >55 yrs, tumor >4 cm, aggressive histology variant, prior Hx of
RT, N+, extrathyroid extension.

50
Q

In addition to improved LC, what is another reason to advocate for a total thyroidectomy even in low-risk pts?

A

It allows for easier f/u with whole-body iodide scans and serum thyroglobulin (Tg).

51
Q

Per NCCN guidelines (2018), what are 3 indications for recommending adj Tx after GTR in DTCa?

A

Indications for adj Tx after GTR in DTCa are (if any present):

  1. > 4-cm tumor
  2. Extrathyroidal extension
  3. Postop unstimulated Tg >5–10 ng/mL
52
Q

What are the 5 aggressive histologic subtypes of DTCa that merit consideration of adj Tx?

A

Aggressive histologic subtypes that merit consideration of adj Tx are:

  1. Tall cell
  2. Columnar cell
  3. Hobnail
  4. Poorly differentiated
53
Q

Generally, what is the adj Tx paradigm for DTCa?

A

DTCa adj Tx paradigm: long-term TSH suppression alone or with I-131 +/- EBRT

54
Q

What are the indications for adj I-131 in addition to TSH suppression for DTCa?

A

Suspected or proven residual normal thyroid tissue or residual tumor, are indications for adj I-131.

55
Q

What is the mCi dose range to ablate residual normal thyroid tissue?

A

30 mCi is as effective as 100 mCi to ablate residual normal thyroid tissue in low-risk DTCa. (Mallick U et al., NEJM 2012)

56
Q

What is the mCi dose range to ablate a residual TCa Dz?

A

The dose to ablate a residual TCa lesion is 100–200 mCi.

57
Q

What are the 4 indications for adj EBRT in addition to TSH suppression and I-131 in TCa?

A

Indications for adj EBRT in addition to TSH suppression and I-131 are:

  1. pT4 papillary and ≥55 yo
  2. Gross residual Dz in the neck after I-131
  3. Bulky mets after I-131
  4. Lesions with inadequate iodide uptake
58
Q

What 3 regions should be irradiated with EBRT in a pt ≥55 yo with pT4 papillary TCa?

A

Thyroid bed, bilat neck, and the upper mediastinal nodes

59
Q

What is the prognosis for pts with locoregional vs. distant recurrence of DTCa?

A

The prognosis is excellent if recurrence is locoregional (long-term OS is 80%–90%). It is much worse with distant recurrences.

60
Q

What are the typical EBRT doses for DTCa?

A

Gross Dz: 66–70 Gy, positive margins: 63–66 Gy
Microscopic Dz: 60 Gy
Nodal basins: 50–54 Gy

61
Q

What is a systemic salvage option for I-131 refractory DTCa?

A

Kinase inhibitors significantly improve PFS. (Schlumberger M et al., NEJM 2015)

62
Q

Generally, what is the Tx paradigm for medullary TCa?

A

Medullary TCa Tx paradigm: definitive Sg; EBRT for

palliation/unresectable Dz

63
Q

Generally, what is the Tx paradigm for anaplastic TCa?

A

Anaplastic TCa Tx paradigm: max safe resection → adj CRT; taxane, and/or doxorubicin with conventional or hyperfractionated EBRT (Smallridge RC et al., Thyroid 2012)

64
Q

For which group of anaplastic TCa pts does PORT improve survival?

A

Per recent SEER analysis (Chen J et al., Am J Clin Oncol 2008), PORT improved survival in pts with extrathyroid extension of Dz but not for those with thyroid-confined or metastatic Dz.

65
Q

What are the acute side effects of >100 mCi of I-131?

A

GI irritation, sialadenitis, and cystitis

66
Q

What are the 3 most important long-term side effects of >100 mCi of I-131?

A

Pulmonary fibrosis, oligospermia, and leukemia

67
Q

What does the f/u of TCa pts entail?

A

TCa f/u: H&P + TSH/Tg levels at 6 and 12 mos, then annually if no Dz; neck US; TSH-stimulated iodine scans if clinically indicated (NCCN 2018)

68
Q

What kind of additional imaging can be considered if the I-131 scan is negative but the stimulated Tg level is elevated?

A

If the I-131 scan is negative but the stimulated Tg level is elevated, neck US or CT with contrast can be considered.

69
Q

What is the max recommended lifetime dose for I-131?

A

The max recommended lifetime dose is 800–1,000 mCi.

Radiation Oncology Residency (44 decks)

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