Thyroid Cancer Flashcards
What are the different histological classifications of thyroid cancer?
Papillary (76%), follicular (17%), medullary (3%), anaplastic (2%), other (2%)
What does differentiated thyroid cancer refer to?
Papillary and follicular variants = most take up and secrete thyroglobin, TSH driven
What is the link between differentiated features and prognosis?
Differentiated features mean good prognosis compared to other solid tumours
What is the epidemiology of differentiated thyroid cancer?
Uncommon in children and Afro-Americans, more common in men
Rates increase from age 15-40 in females then plateaus
Rises steadily with age in men
What are some associations of differentiated thyroid cancer?
Strong = radiation Weak = thyroid adenomata, conditions associated with chronic TSH elevation, increasing parity
What are some factors that are not linked to differentiated thyroid cancer?
Diet, family history, other proven malignancies, smoking, other lifestyle factors
How do differentiated thyroid cancers present?
Majority present with palpable nodules
Small percentage are change findings
About 5% present with local or disseminated metastases
What are some features of papillary thyroid cancer?
Comments next histological type, associated with Hashimoto’s thyroiditis, prognosis generally very good with 10 year mortality <5%
How does papillary thyroid cancer spread?
Tends to spread via lymphatics
May spread haematogenously to lungs, bone, liver and brain
What are some features of follicular carcinomas?
Second most common histological type, incidence slightly raised in regions of relative iodine deficiency, prognosis similar to that of papillary cancer
How do follicular carcinomas spread?
Tend to spread haematogenously
Lymphatic spread and gene lymph node enlargement are rare
How are differentiated thyroid cancers investigated?
Usually involves US-guided FNA of lesion, can involve excision biopsy of lymph node
What investigations are useless for differentiated thyroid cancer?
Isotope thyroid scan, CT, MRI
What investigation should be done if vocal cord palsy is suspected clinically?
Pre-operative laryngoscopy
What are the clinical predictors of malignancy?
New thyroid nodule age <20 or >50 Male Nodule increasing in size Lesion >4cm diameter History of year and neck irradiation Vocal cord palsy
What is the treatment of choice for differentiated thyroid cancers?
Surgery = thyroid lobectomy with isthmusectomy, sub-total or total thyroidectomy
What is the AMES risk stratification system?
Used to stratify patients as high or low risk = age, metastases, extent of primary tumour, size of primary tumour
What patients are classed as AMES low risk?
Younger patients (men<40, women<50) with no evidence of metastases Older patients with intrathyroidal papillary lesion Older patients with minimally invasive follicular lesion and primary tumour <5cm and no distant metastases
What is the 20 year survival of patients in each AMES risk group?
Low = 99% High = 61%
What patients are classed as AMES high risk?
All patients with distant metastases
Extrathyroid disease in patients with papillary cancer
Significant capsular invasion with follicular carcinoma
Primary tumour >5cm in older patients
What patients are treated with a thyroid lobectomy with isthmusectomy?
Papillary microcarcinoma (<1cm diameter)
Minimally invasive follicular carcinomas with capsular invasion only
AMES low risk
What patients are treated with sub-total or total thyroidectomy?
DTC with extra-thyroidal spread DTC with distant metastases Bilateral/multifocal DTC DTC with nodal involvement AMES high risk
How common is lymph node spread at diagnosis in differentiated thyroid cancer?
Papillary = 35-60% Follicular = 20%
What patients should undergo nodal clearance?
Patients with macroscopic lymph node disease
How is lymph node involvement treated?
Papillary = central compartment clearance and lateral lymph node sampling Follicular = central lymph node clearance
When should calcium he checked post-op?
Within 24hrs = replacement initiated if corrected calcium falls below 2mmol/L
When should IV calcium be given?
When levels fall below 1.8mmol/L
What medication are patients discharged on after surgery?
T3 or T4
When is whole body iodine scanning used?
In patients who have undergone sub-total or
total thyroidectomies = usually 3-6 months post-op
What must be stopped before a whole body iodine scan?
T4 = stopped 4 weeks before scan T3 = stopped 2 weeks before scan
Why is rhTSH a better measure for whole body iodine scans?
No need to stop T3 or T4
What should TSH levels be to give the best results in a whole body iodine scan?
Greater than 20 = sensitivity determined by ensuring TSH is elevated
How are whole body iodine scans carried out?
rhTSH injections have n Monday/Tuesday
75-150 MBq I-131 administered as capsule on Wednesday
Patient returns for imaging on Friday
What are the results of whole body iodine scans used for?
Informing treatment decision
How is thyroid remnant ablation carried out?
Patient admitted to lead lined room with mains sewerage, pre-treated with rhTSH before procedure, 2-3 GBq capsule of I-131 administered
What are some side effects of thyroid remnant ablation?
Sialadenitis, sore throat
What precautions are in place during thyroid remnant ablation?
Patient uses disposable cutlery, sheets and clothes stored until safe
Little or no contact with nurses and visitors
When are patients discharged after a thyroid remnant ablation?
When count rate <500cps at 1m
How much radiation is excreted in the first 24hrs after thyroid remnant ablation?
80% = significant radiation protection regulations
What do patients normally undergo before they are discharged after thyroid remnant ablation?
Post-therapy scan = maintained on T4 after therapy and scan
What is the aim of thyroid remnant ablation?
Suppress TSH < 0.1mU/l and have FT4 below 25
What is the rationale behind thyroid remnant ablation?
Ablate residual thyroid tissue in order to destroy occult microfoci
Remove residual thyroid tissue which may be a source of Tg and therefore confound the levels during follow up
What does thyroid remnant ablation allow?
Predictively useful scanning in whole body scans and subsequent high dose therapy if required
What are the long term effects of thyroid remnant ablation?
Small but significant increase in incidence of AML = mainly in patients with cumulative I-131 doses >800mCi and repeated therapy doses within 12 months
That can thyroglobin (Tg) be used as?
Tumour marker = raised TSH is associated with elevated Tg so results can be affected by thyroid status
What may occur is anti-thyroid antibodies are measured at the same time as a titre?
May affect interpretation of results
When should thyroglobin be measured?
Pre-op = not all patients secrete Tg
What is the 10 year survival of differentiated thyroid cancer?
Papillary = 95% Follicular = 88%
How is recurrent disease detected?
Rising Tg and imaging
What commonly causes recurrence in cervical lymph nodes?
Papillary cancer
What commonly causes haematogenous spread?
Follicular cancer = lungs, bone and brain
What is the recurrent rate of differentiated thyroid cancer?
30%
What is the difficult patient group in recurrent disease?
Rising Tg but negative whole body I-131 scan = PET scans used to identify disease sites and allow targeted treatment
