Thyroid Flashcards
What are the main histological subtypes of thyroid cancer? (In order of frequency?)
Papillary (75-85%)
Follicular (10-20%)
Poorly differentiated (5%)
Anaplastic (<2%)
Medullary (5-10%)
Others (lymphoma, mets, small cell)
What histopathological subtypes are classed as differentiated?
Papillary
Follicular
Where does medullary thyroid cancer originate?
In C cells (can secrete calcitonin)
What familial syndrome is medullary thyroid cancer associated with?
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.
Describe the T staging for thyroid cancer? (TNM8)
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
Describe the N staging for thyroid cancer?
N1a level VI nodes
N1b cervical/retropharyngeal/superior mediastinal nodes
How to investigate a thyroid mass?
Bloods
Hx and examination
USS
FNA
Describe the Ultrasound staging system of thyroid nodules
U1 - 5
U1 normal U2 benign U3 equivocal U4 suspicious U5 malignant
Describe the FNA grading system?
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
What are the definite indications for total thyroidectomy
>4cm (>=T3) Multi-focal Extra thyroidal spread Family history Lymph node involvement/distant mets
Who should definitely be offered radioiodine remnant ablation?
Tumour >4cm
Any size with gross extrathyroid extension,
lateral neck nodes
Who should not get RAI adjuvantly?
Solitary <=1cm
Histology classical PTC or follicular variant of papillary or follicular ca
Minimally invasive
No invasion of thyroid capsule
How is iodine131 excreted?
75% excretion via urine
Should double flush toilet for 1 week
Consideration of practicalities for incontinent patients
What is the half life of iodine 131?
8 days
Effective half life 24h
What types of thyroid cancer is Iodine131 used in?
Differentiated (papillary or follicular)
What dose of radioiodine is used adjuvantly?
T1&T2 : 1.1 GBq
T3, T4, N1 : 3.5GBq
What should the TSH be during treatment?
> 30
TSH stimulation is given for 2 days pre treatment (thyrogen IM)
What dietary considerations should patients be advised about with Iodine131?
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
What are the acute side effects of iodine 131?
Sore throat
Neck swelling
Nausea
Bleeding/oedema in mets
What should patients be advised about regarding pregnancy with iodine131
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
What are the late SE of iodine131?
1:20 risk of dry mouth
<1% risk of secondary malignancy
What dose of I131 is used in metastatic/residual disease? And how frequent can doses be given?
5.5GBq
At least 6/12 apart
What is the max cumulative dose of I131?
22GBq
How long should patients avoid bloods/invasive procedures after receiving radioiodine?
1 month
Inform lab of urgent samples needed
What advice should be given to breastfeeding patients prior to radioiodine
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
What follow up should be done post ablation?
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
What is dynamic risk stratification?
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
What percentage of differentiated thyroid cancer develop mets?
7-23%
What are the common sites of metastatic disease? (Differentiated)
Neck nodes, lung, bone
What is the first treatment for metastatic disease?
Thyroidectomy
Following thyroidectomy for metastatic disease (differentiated), what is first line treatment?
Radioiodine. This can be repeated if >6/12
What should you consider when giving pre-radioiodine TSH stimulation in metastatic patients?
Prophylactic steroids to cover for tumour flare
What is classed as radioiodine refractory disease?
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)
What is the prognosis of radioiodine refractory disease?
MOS 2.5-3.5y
If giving radioiodine with spinal mets. What should you consider?
Irradiating spine first as can cause oedema
What dose of radiotherapy would you give for thyroid cancer?
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
What treatment options can be considered in radioiodine refractory disease?
Surveillance XRT Surgery Supportive care Trials TKIs - levantinib or sorafenib
Would you give radioiodine to a metastatic anaplastic thyroid cancer?
No, no role for radioiodine.
What is the median survival of anaplastic thyroid cancer?
7 months
What are the treatment options for anaplastic thyroid cancer?
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
What blood marker should be checked for medullary thyroid cancer?
Calcitonin (NOT Tg)
CEA
What adjuvant treatment is offered for medullary thyroid cancer?
No proven benefit for adjuvant treatment
No need for TSH suppression, just replace
What should you screen for in medullary thyroid cancer?
Phaeochromocytoma
Genetics referral for RET
What systemic treatment can be considered for metastatic medullary thyroid ca?
Cabozantinib 140mg OD.
Prolongs PFS (11.2m v 4m) RR 30%
