Genetic Diagnosis and Prophylactic Surgery for Inherited Medullary Thyroid Carcinoma

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Out of a total of 634 MTC pts, 175 pts had MEN 2A, 49 had FMTC, 20 had MEN 2B, and 390 had sporadic MTC in a nationwide questionnaire survey. The respective 5- and 20-year survival rates were 96.9% and 93.9% in MEN 2A, 100% and 97.1% in FMTC, 73.8% and 24.6% in MEN 2B, and 90.8% and 79.0% in sporadic MTC, (p<0.05 except MEN 2A vs FMTC), 94.8% and 88.2% in women, 87.0% and 60.3% in men (p<0.0001), 94.6% and 83.1% in pts <50 years of age and 90.6% and 81.1% in pts <50 years old (p=0.0045). MND, FMTC, men, ≧50 years of age and early stage patients had a better outcome.Mutations were found in 47 of 47 MEN 2A families and five of the six FMTC families examined. RET proto-oncogene are related to the disease phenotype. A mutation at codon 918 was found in germline DNAs of all four pts with MEN 2B and somatic mutations in seven of the 17 pts sporadic MTC pts. Patients with 918 somatic mutation showed a significant lower survival rate than patients without 918 mutation (p=0.035). Early mutation detectioin also provides an opportunity to plan surgery for MTC although questions remain regarding the appropriate age of surgery. The decision as to the timing of surgery should be based on the site of the mutated codon and estimation of the degree of malignancy of the disease.