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MariannaViukari
CamillaSchalin-Jäntti

Primary Care Follow-Up of Thyroid Cancer after Treatment

Essentials

  • Papillary or follicular thyroid cancer is followed up in specialized care for 1-5 years after treatment, depending on the disease prognosis. Follow-up can subsequently be continued in primary health care if the patient is considered to be disease free. Country-specific variation may exist. Find out about local policies and practices.
  • Hypothyroidism in a patient monitored in primary health care should be treated according to the usual principles. The TSH target of patients considered to be disease free is normally 0.5-2 mU/l. In elderly people, higher TSH levels are acceptable.
  • Individual recommendations for monitoring should be recorded in the discharge summary from specialized care.

Epidemiology of thyroid cancer

  • Globally, the age-standardized incidence rates of thyroid cancer were about 10/100 000 women and 3/100 000 men in 2020 http://www.thelancet.com/journals/landia/article/PIIS2213-8587%2822%2900035-3/fulltext. Significant differences exist between countries and the incidence is typically higher in developed countries.
  • Papillary and follicular carcinomas represent more than 90% of all thyroid cancers. They both have a favourable prognosis.
  • The large majority of metastases are detected within 3 years of cancer therapies. According to a Finnish study, about 10.3% of the patients experience a disease recurrence during follow-up of 16 years. The majority of the recurrences are diagnosed within 10 years. The most common site for metastases is the neck lymph nodes.

Treatment of thyroid cancer

  • Thyroidectomy is the most common initial treatment. For small tumours, lobectomy may be sufficient.
  • After thyroidectomy, a significant share of patients is given radioiodine therapy. The need for treatment and the dose are assessed based on factors such as tumour size and disease stage.
    • For single tumours less than 1 cm in diameter, for example, surgery alone is sufficient and no radioiodine therapy is needed.
    • After lobectomy, radioiodine therapy is not given.

Thyroxine after cancer treatment

  • After thyroidectomy, patients need lifelong thyroxine treatment. After lobectomy, thyroxine is not necessarily needed unless the patient develops hypothyroidism.
  • Patients considered free of disease should receive thyroxine in doses routinely used in normal hypothyroidism whilst monitoring the TSH and free T4 levels.
  • If residual cancer is known or suspected to exist, the aim is to suppress its growth with excess thyroxine and to keep TSH concentration lower than usual. These patients should be managed in specialized care.
    • Even if the aim is to lower TSH to a low level, patients should not develop symptoms of hyperthyroidism affecting their quality of life. In patients with cardiac disease or those of advanced age, higher TSH levels often have to be accepted.
    • Prolonged subclinical thyrotoxicosis may predispose postmenopausal women to osteoporosis and any patient to atrial fibrillation or left ventricular hypertrophy.
    • Thyroxine replacement should be reduced no later than when follow-up is to be continued in primary health care.

Follow-up in specialized care

  • All patients are followed up in specialized care for 1-5 years from the end of treatment, and those considered to have no residual cancer can subsequently be transferred to primary health care. Find out about local practices.
  • Patients with known or suspected residual cancer are managed for at least 10 years or permanently in specialized care. These patients typically have tumour growth outside the thyroid gland and vascular invasion detected in the histopathological diagnosis.
    • This group includes patients with detectable levels of stimulated thyroglobulin in the assessment of response after thyroidectomy and radioiodine therapy. Moreover, imaging studies may be suggestive of residual cancer.

Follow-up in primary health care

  • When follow-up is transferred from specialized care to primary health care, the final assessment in specialized care should define the TSH target and provide other recommendations for follow-up.
  • In patients found to be disease free, the TSH target is normally 0.5-2 mU/l and free T4 should be within the reference range. Elderly patients free of disease have higher TSH targets, normally the age-appropriate reference range.
  • Adjustment of the thyroxine dose should follow the normal principles for treating hypothyroidism; see article Hypothyroidism Hypothyroidism.
  • TSH and free T4 should be measured every 1-2 years, as far as possible with palpation of the neck.
  • If a lump develops on the neck, clinical assessment and neck ultrasonography (US) should be performed. A fine needle sample should be taken and the serum thyroglobulin level measured, as necessary.
  • Routine neck US and thyroglobulin measurement may be recommended for some high-risk or young patients 10 and 15-20 years from diagnosis, for example. Specialized care will provide the required instructions when follow-up is transferred to primary health care.
  • After radioiodine therapy, serum thyroglobulin should be undetectable or remain at the previous level if the patient did not receive radioiodine therapy. Thyroglobulin antibodies (normally undetectable) should be measured at the same time to ensure the reliability of the test.
    • If thyroglobulin antibodies are detected, specialized care should be consulted.
  • Specialized care should be consulted if neck palpation, verified with neck US and a fine needle sample, gives rise to a suspicion of lymph node metastasis or local recurrence or if the serum thyroglobulin level increases.

References

  • Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid 2016;26(1)1-133. [PubMed]
  • Pelttari H. Long-term outcome of patients with low-risk papillary or follicular thyroid carcinoma. Academic dissertation. University of Helsinki, Helsinki 2012 http://helda.helsinki.fi/items/214e31f0-c85e-4c88-bb96-81fd30ed8d61.