Thyroid

Question 1

What are the main histological subtypes of thyroid cancer? (In order of frequency?)

Answer 1

Papillary (75-85%)
Follicular (10-20%)
Poorly differentiated (5%)
Anaplastic (<2%)

Medullary (5-10%)
Others (lymphoma, mets, small cell)

Question 2

What histopathological subtypes are classed as differentiated?

Answer 2

Papillary

Follicular

Question 3

Where does medullary thyroid cancer originate?

Answer 3

In C cells (can secrete calcitonin)

Question 4

What familial syndrome is medullary thyroid cancer associated with?

Answer 4

MEN2A or MEN2B
(20% of cases)

MEN2: autosomal dominant inherited disorder characterised by medullary thyroid cancer, parathyroid tumours and pheochromocytoma. MEN results from germ line mutations in the REt proto-oncogene.

MEN2B is less common than 2A and is characterised by more aggressive MTC (100% cases), pheo (50-%), mucosal neuromas (95-98%) and intestinal ganglion neuromas (40%). Hyperparathyroidism is absent (unlike 2A). Nearly all patients have a marfanoid habitus. Early total thyroidectomy is effective in preventing MTC.

Question 5

Describe the T staging for thyroid cancer? (TNM8)

Answer 5

T1 <=2cm
T1a <=1cm. T1b 1-2cm
T2. >2cm <=4cm
T3a >4cm limited to thyroid
T3b. Any size with gross extrathyroidal extension
T4a beyond capsule and invading local tissues
T4b invades prevertebral fascia/encases carotid artery or mediastinal vessels

Question 6

Describe the N staging for thyroid cancer?

Answer 6

N1a level VI nodes

N1b cervical/retropharyngeal/superior mediastinal nodes

Question 7

How to investigate a thyroid mass?

Answer 7

Bloods
Hx and examination
USS
FNA

Question 8

Describe the Ultrasound staging system of thyroid nodules

Answer 8

U1 - 5

U1 normal
U2 benign
U3 equivocal
U4 suspicious
U5 malignant

Question 9

Describe the FNA grading system?

Answer 9

Thy 1-5

Thy 1 - non-diagnostic, need repeat
Thy2 - benign
Thy3A - atypical, can’t exclude malignancy and further Ix required
Thy3f - follicular neoplasm suspected, need diagnostic hemithyroidectomy
Thy4 - suspicious of malignancy - need diagnostic hemithyroidectomy
Thy5 - malignant - thyroidectomy

Question 10

What are the definite indications for total thyroidectomy

Answer 10

>4cm (>=T3)
Multi-focal
Extra thyroidal spread
Family history
Lymph node involvement/distant mets

Question 11

Who should definitely be offered radioiodine remnant ablation?

Answer 11

Tumour >4cm
Any size with gross extrathyroid extension,
lateral neck nodes

Question 12

Who should not get RAI adjuvantly?

Answer 12

Solitary <=1cm
Histology classical PTC or follicular variant of papillary or follicular ca
Minimally invasive
No invasion of thyroid capsule

Question 13

How is iodine131 excreted?

Answer 13

75% excretion via urine

Should double flush toilet for 1 week
Consideration of practicalities for incontinent patients

Question 14

What is the half life of iodine 131?

Answer 14

8 days

Effective half life 24h

Question 15

What types of thyroid cancer is Iodine131 used in?

Answer 15

Differentiated (papillary or follicular)

Question 16

What dose of radioiodine is used adjuvantly?

Answer 16

T1&T2 : 1.1 GBq

T3, T4, N1 : 3.5GBq

Question 17

What should the TSH be during treatment?

Answer 17

> 30

TSH stimulation is given for 2 days pre treatment (thyrogen IM)

Question 18

What dietary considerations should patients be advised about with Iodine131?

Answer 18

2/52 low iodine diet pre treatment

Not to have CT contrast for 8/52 prior and no amiodarone for a year prior to tx

Question 19

What are the acute side effects of iodine 131?

Answer 19

Sore throat
Neck swelling
Nausea
Bleeding/oedema in mets

Question 20

What should patients be advised about regarding pregnancy with iodine131

Answer 20

Avoid pregnant people for set time after treatment (up to 3/52)
Not to become pregnant for 6/12 or father a child within 4/12

Question 21

What are the late SE of iodine131?

Answer 21

1:20 risk of dry mouth

<1% risk of secondary malignancy

Question 22

What dose of I131 is used in metastatic/residual disease? And how frequent can doses be given?

Answer 22

5.5GBq

At least 6/12 apart

Question 23

What is the max cumulative dose of I131?

Answer 23

22GBq

Question 24

How long should patients avoid bloods/invasive procedures after receiving radioiodine?

Answer 24

1 month

Inform lab of urgent samples needed

Question 25

What advice should be given to breastfeeding patients prior to radioiodine

Answer 25

Stop breast feeding at least 8/52 prior to tx and don’t restart after treatment Breast feeding risks iodine uptake in lactating breasts and increases long term risk of breast cancer

Question 26

What follow up should be done post ablation?

Answer 26

Residual/metastatic disease - SPECT scan 2-10 days post ablation ``` For non-metastatic patients: TSH suppression (TSH <0.1 until post tx scan), serum thyroglobulin and antibodies at 3/12 ``` Dynamic risk stratification at 9/12 Then follow up every 6-12 months. Clinical exam of neck, TFTs and Tg (and antibodies). USS if Tg antibody positive. Tg should be <1 if rises, USS neck +\- FNA and CT thorax. If normal - PET

Question 27

What is dynamic risk stratification?

Answer 27

Informs future TSH suppression, done at 9/12 post tx USS and stimulated Tg Low risk (aim TSH 0.3-2): Tg < 1, USS normal Intermediate risk (aim TSH 0.1-0.5 for 5-10y then reassess): Tg 1-10, USS equivocal High risk (TSH <0.1): Tg >10, USS abnormal

Question 28

What percentage of differentiated thyroid cancer develop mets?

Answer 28

7-23%

Question 29

What are the common sites of metastatic disease? (Differentiated)

Answer 29

Neck nodes, lung, bone

Question 30

What is the first treatment for metastatic disease?

Answer 30

Thyroidectomy

Question 31

Following thyroidectomy for metastatic disease (differentiated), what is first line treatment?

Answer 31

Radioiodine. This can be repeated if >6/12

Question 32

What should you consider when giving pre-radioiodine TSH stimulation in metastatic patients?

Answer 32

Prophylactic steroids to cover for tumour flare

Question 33

What is classed as radioiodine refractory disease?

Answer 33

At least 1 measurable lesion with no uptake on Iodine 131 scan PD within 12/12 of iodine 131 despite uptake at the time PD after 600mCi (3.7 GBq = 100mCi)

Question 34

What is the prognosis of radioiodine refractory disease?

Answer 34

MOS 2.5-3.5y

Question 35

If giving radioiodine with spinal mets. What should you consider?

Answer 35

Irradiating spine first as can cause oedema

Question 36

What dose of radiotherapy would you give for thyroid cancer?

Answer 36

60Gy in 30# to primary tumour and involved nodes 54Gy in 30# to selected regional nodes Up to 64Gy to macroscopic residuum Reserved for inoperable/non radioiodine avid

Question 37

What treatment options can be considered in radioiodine refractory disease?

Answer 37

``` Surveillance XRT Surgery Supportive care Trials TKIs - levantinib or sorafenib ```

Question 38

Would you give radioiodine to a metastatic anaplastic thyroid cancer?

Answer 38

No, no role for radioiodine.

Question 39

What is the median survival of anaplastic thyroid cancer?

Answer 39

7 months

Question 40

What are the treatment options for anaplastic thyroid cancer?

Answer 40

Very aggressive, often inoperable. BSC Palliative EBRT Palliative chemo (carbo-taxol) - 15% RR BRAF mutated disease - compassionate access programme - dabrafenib/trametinib if PS 0-1

Question 41

What blood marker should be checked for medullary thyroid cancer?

Answer 41

Calcitonin (NOT Tg) | CEA

Question 42

What adjuvant treatment is offered for medullary thyroid cancer?

Answer 42

No proven benefit for adjuvant treatment | No need for TSH suppression, just replace

Question 43

What should you screen for in medullary thyroid cancer?

Answer 43

Phaeochromocytoma | Genetics referral for RET

Question 44

What systemic treatment can be considered for metastatic medullary thyroid ca?

Answer 44

Cabozantinib 140mg OD. ``` Prolongs PFS (11.2m v 4m) RR 30% ```