Evolving paradigms for successful molecular imaging of medullary thyroid carcinoma

Excerpt

Medullary thyroid cancer (MTC) is a rare, neuroendocrine tumour (NET) of parafollicular C cells comprising 5–8% of all thyroid cancers with variable biological behaviour and prognosis [1]. Overall mean survival in MTC is 75–85% at 10 years [1‐3]. Management of both hereditary (20–30%) and sporadic MTC is challenging due to early cervical lymph node metastases occurring in 50% of patients and distant metastases to the liver, lung and bones being found in 10–20% at diagnosis [1, 3]. MTC secretes several neuroendocrine peptides, of which calcitonin (Ct) and less-specific carcinoembryonic antigen (CEA) are useful tumour markers for diagnosis, surveillance and prognosis. Yet despite the high sensitivity of an elevated serum Ct value as a predictor of disease presence, MTC is an elusive and notoriously problematic tumour to image [1, 3]. Anatomy-based imaging with CT and MRI has exhibited limited sensitivity due to the frequent small size of the metastatic deposits. Although a variety of specific and nonspecific scintigraphic techniques such as ²⁰¹Tl, ^99mTc-sestamibi, ^99mTc-tetrofosmin, ¹³¹I/¹²³I-metaiodobenzylguanidine, ^99mTc-(V)dimercaptosuccinic acid (DMSA), and ¹¹¹In-octreotide have been used to image MTC, none has emerged as the imaging technique of choice [4, 5]. This raises the question as to why we have been unable to successfully image MTC. …