What is the standard treatment approach for thyroid cancer?

Standard Treatment Approach for Thyroid Cancer

The standard treatment for thyroid cancer is total or near-total thyroidectomy followed by radioactive iodine ablation for most cases, except for very low-risk tumors under 1 cm with favorable characteristics. 1, 2

Types of Thyroid Cancer and Initial Evaluation

Thyroid cancer is classified into several main types:

• Differentiated thyroid cancer (DTC) - 90% of cases
  • Papillary (84%)
  • Follicular (4%)
  • Oncocytic/Hürthle cell (2%)
• Medullary thyroid cancer (MTC) - 5-8%
• Poorly differentiated thyroid cancer - 5%
• Anaplastic thyroid cancer (ATC) - 1%

Initial evaluation should include:

• Thyroid function tests (TSH, free T4)
• Ultrasound of thyroid and central neck
• Fine-needle aspiration cytology (FNAC) of suspicious nodules
• For MTC: calcitonin and CEA measurements 1, 2

Treatment Algorithm for Differentiated Thyroid Cancer

1. Surgical Management

• Total or near-total thyroidectomy is recommended for:

  • Tumors >1 cm
  • Multifocal disease
  • Bilateral disease
  • Extrathyroidal extension
  • Familial disease
  • Lymph node involvement
  • Distant metastases 1, 2

• Less extensive procedures may be acceptable only for:

  • Unifocal tumors <1 cm
  • Intrathyroidal location
  • Favorable histology
  • No extrathyroidal extension
  • No lymph node metastases 2

• Lymph node dissection:

  • Central compartment neck dissection for clinical/radiological evidence of involvement
  • Lateral compartment dissection for lateral metastases 1, 2

2. Post-Surgical Radioactive Iodine (RAI) Ablation

• Recommended for all patients except very low-risk cases
• Effective thyroid ablation requires adequate TSH stimulation
• Recombinant human TSH (rhTSH) is approved for preparation for RAI ablation
• Lower dose of 1850 MBq (50 mCi) is as effective as 3700 MBq (100 mCi) 1

3. Thyroid Hormone Therapy

• Initiated immediately after surgery with dual aims:
  • Replace thyroid hormone
  • Suppress potential TSH stimulation of tumor cells
• TSH suppression targets:
  • High-risk: <0.1 mU/L
  • Intermediate-risk: 0.1-0.5 mU/L
  • Low-risk: 0.5-2.0 mU/L (lower normal range) 1, 2

Treatment of Medullary Thyroid Cancer (MTC)

1. Preoperative evaluation:

   • Basal serum calcitonin, CEA, calcium
   • Plasma metanephrines/normetanephrines
   • Imaging: neck US, chest CT, liver CT/MRI for advanced disease 1

2. Surgical management:

   • Total thyroidectomy with bilateral central lymph node dissection
   • Lateral neck dissection for positive nodes
   • Less aggressive surgery for distant metastatic disease to preserve function 1

3. Post-surgical management:

   • Replacement thyroxine to maintain normal TSH
   • Regular monitoring of calcitonin and CEA levels 1

Treatment of Anaplastic Thyroid Cancer (ATC)

ATC is extremely aggressive with poor prognosis (median survival ~4 months). Treatment includes:

• Surgery if resectable
• External beam radiotherapy
• Systemic therapy 1

Advanced/Metastatic Disease Management

For locally recurrent or metastatic, progressive, radioactive iodine-refractory disease:

• Lenvatinib is FDA-approved and has shown significant response rates 3, 4
• Other tyrosine kinase inhibitors (sorafenib, cabozantinib) may be used 4
• Targeted therapies directed at specific mutations (BRAF, RET, NTRK) are increasingly used 4

Follow-up and Monitoring

• Regular serum thyroglobulin (Tg) measurements (not sooner than 6 weeks post-surgery)
• TSH monitoring and adjustment of levothyroxine dose
• Neck ultrasound
• Post-therapy dynamic risk stratification at 9-12 months to guide further management 1, 2

Important Considerations

• Surgical complications such as laryngeal nerve palsy and hypoparathyroidism are rare (<1-2%) when performed by experienced surgeons 2
• RAI therapy is generally well-tolerated with few long-term adverse effects
• Long-term follow-up is recommended for all patients with thyroid cancer 1
• Recurrent disease should be managed surgically whenever possible 1

The treatment approach should be tailored based on the specific type of thyroid cancer, stage, and risk factors, with the primary goal of optimizing survival and quality of life.