Differentiated Thyroid Cancer

Question 1

What is Differentiated Thyroid Cancer (DTC)?

Answer 1

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

Differentiates means good prognosis, generally

Question 2

Characteristics of DTCs?

Answer 2

Most take up iodine and secrete thyroglobulin

DTCs are TSH driven

Question 3

Occurrence of DTCs?

Answer 3

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

Question 4

Lifestyle in relation to DTC?

Answer 4

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

Question 5

Presentation of DTC?

Answer 5

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

Question 6

Spread of papillary thyroid carcinoma?

Answer 6

Tends to spread via LYMPHATICS

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

Question 7

Assoc. diseases with papillary thyroid cancer?

Answer 7

Assoc. with Hashimoto’s thyroiditis

Question 8

Spread of follicular thyroid carcinoma?

Answer 8

Tends to spread HAEMATOGENOUSLY

Lymphatic spread and lymph node enlargement are relatively rare

Question 9

Assoc. problems with follicular carcinoma?

Answer 9

Incidence is slightly higher with iodine deficiency

Question 10

Ix of thyroid carcinoma?

Answer 10

Usually, USS-guided FNA of the lesion

May involve excision biopsy of lymph nodes

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

Question 11

Clinical predictors of malignancy?

Answer 11

• 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

Question 12

Treatment of choice for DTC?

Answer 12

Gold standard treatment:

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

Question 13

Surgical options?

Answer 13

Thyroid lobectomy with isthmusectomy (some cancer cells may remain)

Sub-total thyroidectomy (likely the best option)

Total thyroidectomy (risk of damage to other structures)

Question 14

Risk stratification of DTC patients?

Answer 14

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

Question 15

Patient that fall into AMES low risk category?

Answer 15

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

Question 16

Patients that fall into AMES high risk category?

Answer 16

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

Question 17

When might thyroid lobectomy with isthmusectomy be used?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

Use of lymph node surgery?

Answer 19

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

Question 20

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

Answer 20

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

Follicular - central lymph node clearance although the role is unclear

Question 21

Post-operative cautions?

Answer 21

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

Question 22

On discharge, which medications are given?

Answer 22

Discharge on T3 or T4

Question 23

Role of whole body iodine scanning on follow-up?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

Timeline of whole body scanning using rhTSH?

Answer 25

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

Patient return for imaging 2 days later

Question 26

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

Answer 26

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

Question 27

Process of thyroid remnant ablation (TRA)?

Answer 27

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

Administer a higher dose of iodine

Question 28

Side effects of thyroid remnant ablation with iodine?

Answer 28

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

Question 29

Cautions with radioiodine use in-patient?

Answer 29

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

There is little/no contact with staff/visitors

Question 30

When can patients be discharged following radioiodine?

Answer 30

When count rate <500cps at 1 metre

Question 31

Discharge advice with radioiodine?

Answer 31

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

Question 32

Ix following Thyroid remnant ablation and discharge?

Answer 32

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

Question 33

Treatment following TRA?

Answer 33

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

Question 34

Factors that affect thyroglobulin measurement?

Answer 34

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

Question 35

Reasons for using TRA?

Answer 35

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

Question 36

Long-term effects of TRA?

Answer 36

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

Question 37

Ix for recurrent disease?

Answer 37

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

Question 38

Recurrence in the 2 types of DTC?

Answer 38

Recurrence in cervical lymph nodes is more common in papillary cancer

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