Monday, February 27, 2012

Well Differentiated Thyroid Cancer Follow Up

Papillary and/or Follicular thyroid cancer will recur or persist in about 25% of patients, and 80% of these recurrences will be in the neck. Recurrence occurs most commonly in the first 2 years after thyroidectomy. In papillary thyroid cancer, however, recurrence can occur up to 45 years after surgery, whereas virtually all patients with follicular and Hürthle cell cancer recur before 12 years after surgery.
  • Radioiodine ablation is recommended for patients with papillary thyroid cancers larger than 1.5cm, multifocal tumors, and for those with lymph node metastases. 
  • Invasive follicular and Hürthle cell cancer also warrant radioiodine therapy.  
  • Doctors routinely recommend the  use 30 to 50 mCi of radioiodine in low risk and 100 to 200 mCi of radioiodine in high-risk patients. 
  • The initial radioiodine treatment should be performed under hormone withdrawal, or with recombinant TSH stimulation 6-8 weeks post operatively in an iodine deficient patient. 
  • Patients should have a thyroid hormone levels (TSH, T3, T4, Thyroglobulin) measured as well  pregnancy test prior to 131-Iodine scanning and ablation therapy, and post-treatment imaging. 
TSH  is known to stimulate tumor growth, invasion, angiogenesis, and thyroglobulin secretion. Therefore post operatively patients are placed on thyroid hormone replacement therapy. 
  • In  low-risk patients doctors maintain the serum TSH level just below the lower limit of the normal range between 0.1 and 0.4 mU/ mL. 
  • In high-risk patients the dosage is adjusted to maintain a serum TSH level less than 0.1 mU/ mL, as this has been reported to improve tumor free survival. 
Adverse effects of TSH suppression may include:  
External beam radiation and chemotherapy have a limited role in the postoperative management of well differentiated thyroid carcinoma patients
  • External beam radiation is used infrequently in the management of thyroid cancer except as a palliative treatment for locally advanced unresectable disease, positive tumor margins, or recurrent disease after re-resection. 
  • Chemotherapy has shown only minimal benefit in the treatment of well-differentiated thyroid cancer. New clinical trials have recently become available.
Follow-up is different for patients at low, intermediate, and high risk of having persistent or recurrent disease
  • Low risk patients are defined as patients with no local or distant metastases, complete resection of tumor contained within the thyroid with no locoregional invasion, tumor without aggressive histology, and if radioiodine was given there was no uptake outside of the thyroid bed. 
  • Intermediate risk patients have microscopic invasion of tumor into the peri-thyroidal soft tissue at initial surgery or tumor with aggressive histology or vascular invasion. 
  • High-risk patients have macroscopic tumor invasion, incomplete tumor resection, distant metastases, or radioiodine uptake outside the thyroid bed on the post-treatment scan after thyroid remnant ablation.
The absence of persistent disease in patients that have undergone at least a total thyroidectomy and thyroid remnant ablation comprises of no clinical evidence of tumor, no imaging evidence of tumor, and undetectable serum thyroglobulin levels during TSH suppression and stimulation in the absence of interfering antibodies.

All patients with a history of well-differentiated thyroid cancer should have yearly cervical ultrasound scanning, thyroglobulin and thyroglobulin antibodies. 
  • Approximately 20% of patients who are clinically disease free with serum thyroglobulin levels less than 2 ng/mL during thyroid hormone suppression will have a thyroglobulin level greater than 5 ng/mL after rhTSH or thyroid hormone withdrawal. One third of this group will have persistent disease identified on imaging studies. Therefore, a serum thyroglobulin level above 5 ng/mL after rhTSH stimulation is highly sensitive in identifying patients with persistent disease. Furthermore, the clinical significance of minimally detectable thyroglobulin levels is unclear, especially if only detected after TSH stimulation. 
  • Approximately 25% of patients with thyroid cancer have antithyroglobulin antibodies making follow-up with thyroglobulin insensitive. In this group serial serum antithyroglobulin antibody measurements may serve as an imprecise surrogate marker to detect recurrence among these patients. Accurate surveillance for possible recurrence and treatment in patients thought to be free of disease is a major goal of long-term follow-up.

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