Differentiated Thyroid Cancer Flashcards

1
Q

What is Differentiated Thyroid Cancer (DTC)?

A

Umbrella term that refers to papillary (most common) and follicular (2nd most common) variants of thyroid cancer

Differentiates means good prognosis, generally

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2
Q

Characteristics of DTCs?

A

Most take up iodine and secrete thyroglobulin

DTCs are TSH driven

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3
Q

Occurrence of DTCs?

A

Slightly more common in females:
• In females, rates increase from 15-40 years and then plateau
• In males, there is a steady increase with age

There is a lower incidence in Afro-Americans and they are uncommon in childhood; weak assoc. with thyroid adenomata, conditions assoc. with chronic TSH elevation and increasing parity

Strong assoc. with radiation exposure

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4
Q

Lifestyle in relation to DTC?

A

No assoc. with diet, other proven malignancies, FH, smoking or other lifestyle factors

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5
Q

Presentation of DTC?

A

Most present with palpable nodule(s)

Rarely, they can be an incidental finding on histological section of thyroidectomy tissue, i.e: this had been done due to another thyroid problem

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6
Q

Spread of papillary thyroid carcinoma?

A

Tends to spread via LYMPHATICS

There can be haematogenous spread to the lungs, bone, liver and brain

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7
Q

Assoc. diseases with papillary thyroid cancer?

A

Assoc. with Hashimoto’s thyroiditis

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8
Q

Spread of follicular thyroid carcinoma?

A

Tends to spread HAEMATOGENOUSLY

Lymphatic spread and lymph node enlargement are relatively rare

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9
Q

Assoc. problems with follicular carcinoma?

A

Incidence is slightly higher with iodine deficiency

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10
Q

Ix of thyroid carcinoma?

A

Usually, USS-guided FNA of the lesion

May involve excision biopsy of lymph nodes

If vocal chord palsy is clinically suspected, pre-operate laryngoscopy

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11
Q

Clinical predictors of malignancy?

A
  • New thyroid nodule <20 or >50 years of age
  • Male
  • Nodule increasing in size
  • Lesion > 4cm diameter
  • History of head and neck irradiation
  • Vocal cord palsy
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12
Q

Treatment of choice for DTC?

A

Gold standard treatment:

Surgery +/- radioiodine (TRA) + life long follow-up

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13
Q

Surgical options?

A

Thyroid lobectomy with isthmusectomy (some cancer cells may remain)

Sub-total thyroidectomy (likely the best option)

Total thyroidectomy (risk of damage to other structures)

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14
Q

Risk stratification of DTC patients?

A
AMES is used to stratify patient as low or high risk:
Age
Metastases
Extent of primary tumour
Size of primary tumour
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15
Q

Patient that fall into AMES low risk category?

A

Survival is very good in this group:
• Younger patients (men <40, women <50) with no evidence of metastases
• Older patients with intra-thyroidal papillary lesion OR minimally invasive follicular lesion and primary tumour <5cm and no distant metastases

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16
Q

Patients that fall into AMES high risk category?

A

Survival is okay but not as high as in the low risk group:
• All patients with distant metastases
• Extra-thyroidal disease in patients with papillary cancer
• Significant capsular invasion with follicular carcinoma
• Primary tumour >5cm in older patients

17
Q

When might thyroid lobectomy with isthmusectomy be used?

A
  • Patient with a papillary microcarcinoma (<1cm diameter)
  • Minimally invasive follicular carcinoma with capsular invasion only
  • Patients in AMES low risk group
18
Q

When might sub-total thyroidectomy OR total thyroidectomy be used?

A
  • DTC with extra-thyroidal spread
  • Bilateral/multi-focal DTC
  • DTC with distant metastases
  • DTC with nodal inv.
  • Patients in AMES high risk group
19
Q

Use of lymph node surgery?

A

Patients with macroscopic lymph node disease should undergo nodal clearance, bearing in mind that lymph node spread is more common in papillary DTC

There is sampling bias, as not all the nodes are removed

20
Q

Which lymph nodes are removed in the 2 types of DTC?

A

Papillary - central compartment clearance and lateral lymph node sampling for papillary tumours

Follicular - central lymph node clearance although the role is unclear

21
Q

Post-operative cautions?

A

Check calcium within 24 hrs (as parathyroid glands may also be removed)

Ca replacement is initiated if:
• Corrected Ca falls <2 mmol/L

IV Ca is initiated if:
• Calcium levels <1.8 mmol/l
• Symptomatic

22
Q

On discharge, which medications are given?

A

Discharge on T3 or T4

23
Q

Role of whole body iodine scanning on follow-up?

A

Usually performed 3-6 months post-op (used after sub-total/total thyroidectomy)

T4 must be stopped 4 weeks prior to scan and T3 stopped 2 weeks prior

24
Q

Overcoming the need to stop T4/T3 prior to whole body iodine scanning?

A

rhTSH (recombinant human TSH) is better as there is no need to stop T3/T4

This causes a brisk but non-sustained rise in TSH, which makes the cancer cells uptake more iodine

25
Q

Timeline of whole body scanning using rhTSH?

A

Administer rhTSH injections and, the next day, iodine (I-131) is administered as a capsule

Patient return for imaging 2 days later

26
Q

Normal/physiological dark areas (uptake iodine) on whole body iodine scan?

A
  • Salivary glands
  • Gastric mucosa
  • Bladder (due to renal excretion of the iodine)
  • Thyroid remnant (if there is one following surgery)
27
Q

Process of thyroid remnant ablation (TRA)?

A

Pre-treated with rhTSH (as is the case with Ix)

Administer a higher dose of iodine

28
Q

Side effects of thyroid remnant ablation with iodine?

A

Well tolerated but can have:
• Sialadenitis (inflammation of salivary glands; encourage patients to suck mints)
• Sore throat

29
Q

Cautions with radioiodine use in-patient?

A

Patients use disposable; sheets and clothing are stored until they are sage

There is little/no contact with staff/visitors

30
Q

When can patients be discharged following radioiodine?

A

When count rate <500cps at 1 metre

31
Q

Discharge advice with radioiodine?

A

Avoid pregnancy women and children; try to limit contact with other people

32
Q

Ix following Thyroid remnant ablation and discharge?

A

Repeat the whole body scan to ensure uptake in the thyroid bed is <0.1%

Thyroglobulin is used as a tumour marker (only produced by normal or cancerous thyroid cells); this should be measured pre-operatively, as some patients do not secrete thyroglobulin

33
Q

Treatment following TRA?

A

Patients are maintained on T4 following TRA and discharge; aim to suppress the TSH long-term as this results in a better patient prognosis

34
Q

Factors that affect thyroglobulin measurement?

A

May be affected by thyroid status, i.e: raised TSH is assoc. with elevation of Tg levels

Anti-Tg antibodies measured at the same time as the titre may affect interpretation of results

35
Q

Reasons for using TRA?

A
  1. Ablate residual thyroid tissue in order to destroy occult microfoci
  2. Remove residual thyroid tissue (may be a source of Tg and thus confound the levels during follow-up)
  3. Permits useful scanning in whole body scanning and subsequent high-dose therapy, is required
36
Q

Long-term effects of TRA?

A

Small but significant increase in AML (acute myeloid leukaemia); the risk doubles but is still small

If this is going to occur, tends to be ~15 years after

37
Q

Ix for recurrent disease?

A

Rising Tg or by imaging

Some patients can have a rising Tg but -ve whole body I-131 scan; if this is the case, the patient should still be treated for recurrence and a PET scan should be used to identify site of disease and allow surgery/radiotherapy

38
Q

Recurrence in the 2 types of DTC?

A

Recurrence in cervical lymph nodes is more common in papillary cancer

Haematogenous spread to lungs, bone or brain is more common in follicular lesions