This “consensus statement” aims to summarise the current evidence-based knowledge as to “timing” and planning the “extent“ of thyroid surgery in terms of an optimal balance between the prevention of thyroid malignancy (involving metastasis) and the risks associated with more extended surgery (permanent hypoparathyroidism, permanent paralysis of the recurrent laryngeal nerve). Surgery “in time” is influenced by genetic findings and age. Basal (and stimulated) calcitonin levels may individualise the timing and extent of surgery. The review of English-language studies addressing the management of REarranged during Transfection proto-oncogene mutation carriers including the time, extent of thyroid surgery and results. Evidence is mostly obtained from well-designed, non-experimental descriptive investigations, such as comparative, correlation and case–control studies (level III) with a grading of recommendation B, or from expert committee reports or opinions and/or the clinical experience of respected authorities (level IV) with a grading of recommendation C, respectively. “Risk level D” includes multiple endocrine neoplasia 2B cases. Thyroidectomy is recommended within the first year of life, preferably as soon as possible, due to the very early transformation of C cell hyperplasia to more aggressive tumours. Calcitonin levels may be less helpful. In patients with codon 634 mutations (risk level C), thyroidectomy between ages 2 and 4 years has been proposed based upon evidence of age-dependent and codon-specific progression of early medullary thyroid cancer. In “risk level B” (codons 609, 611, 618, 620, 630 and 804), tandem mutation (804–778) patients should undergo thyroidectomy before the age of 6 years. “Risk level A” includes patients with mutations in codons 321, 515, 533, 600, 603, 606, 635, 649, 666, 768, 776, 790, 791, 804 (single mutation), 833, 844, 861, 891 or 912. Surgery may be postponed until the age of 10 years. However, postponing surgery and avoiding central (level VI) neck dissection in patients with risk levels A to C are only justified in families with a less aggressive MTC history and in combination with the results of basal (and calcium- or pentagastrin-stimulated) serum calcitonin levels. The moment of transition from C cell hyperplasia to MTC seems to occur when calcitonin levels rise. In patients with normal basal and stimulated calcitonin levels, the chance of micro-MTC increases significantly. Hereditary C cell disease acts as a model to apply the results of bedside genetic testing, age and calcitonin levels (genotype–age–calcitonin-concept) for the individual timing of thyroid surgery and its extent.
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