Adjuvant Treatment for Medullary Thyroid Carcinoma

Introduction to Adjuvant Radiation Therapy

The National Comprehensive Cancer Network recommends adjuvant radiation therapy for patients with gross extrathyroidal extension (T4a or T4b) with positive margins after resection of all gross disease, or for those with moderate-to-high volume disease in the central or lateral neck lymph nodes with extranodal soft tissue extension 1, 2, 3, 4
Adjuvant external-beam radiation therapy has not been adequately studied, but may provide slight improvements in local disease-free survival for selected patients with extrathyroidal invasion or extensive locoregional node involvement 1, 3

Consider adjuvant external-beam RT for gross extrathyroidal extension (T4a or T4b) with positive margins after resection of all gross disease 1, 2, 3, 4
Consider adjuvant external-beam RT for moderate-to-high volume disease in the central or lateral neck lymph nodes with extranodal soft tissue extension 1, 2, 3, 4

The typical regimen for external-beam RT is 40 Gy in 20 fractions to the cervical, supraclavicular, and upper mediastinal lymph nodes over 4 weeks 1, 2, 3
Subsequent booster doses of 10 Gy in 5 fractions may be given to the thyroid bed 1, 2, 3

All patients require postoperative levothyroxine to normalize TSH 5
Measure basal serum calcitonin and CEA 2-3 months postoperatively to assess for residual disease 1, 2, 3
Approximately 80% of patients with palpable MTC and 50% with nonpalpable but macroscopic MTC have serum calcitonin values indicative of residual disease after supposedly curative resection 1, 2, 3
Calcitonin levels > 1000 pg/mL suggest distant metastases, most likely in the liver 1, 2, 3