A 45-year-old woman with medullary thyroid carcinoma and rising calcitonin after thyroidectomy has negative conventional imaging. Which PET tracer is preferred over FDG for detecting recurrent medullary thyroid carcinoma?
- A 18F-DOPA (6-fluoro-L-DOPA) ✓
- B 18F-FDG (fluorodeoxyglucose)
- C 68Ga-DOTATATE (somatostatin receptor imaging)
- D 18F-NaF (sodium fluoride for bone scanning)
Correct answer: A. 18F-DOPA (6-fluoro-L-DOPA)
Explanation
Medullary thyroid carcinoma (MTC) is a neuroendocrine tumour arising from parafollicular C-cells that express DOPA decarboxylase. 18F-DOPA PET-CT has superior sensitivity (>70%) over FDG (40–55%) for detecting recurrent MTC because MTC uses the L-DOPA pathway for catecholamine synthesis rather than high glucose metabolism. 68Ga-DOTATATE is preferred for well-differentiated neuroendocrine tumours with high somatostatin receptor expression (gastroenteropancreatic NETs, carcinoids) but MTC has variable and often low SSTR expression. 18F-NaF is a bone-specific tracer.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.