Prophylactic thyroidectomy for MEN 2-related medullary thyroid carcinoma based on predictive testing for RET proto-oncogene mutation and basal serum calcitonin in China.

INTRODUCTION: Early and normative surgery is the only curative method for multiple endocrine neoplasia type 2 (MEN 2)-related medullary thyroid carcinoma (MTC).

AIMS: To study the timing of prophylactic total thyroidectomy (TT) for MEN 2-related MTC with different RET mutations in a Chinese population, and to compare the sensitivity and accuracy of fully-automated chemiluminescence immunoassay (FACLIA) and radioimmunoassay (RIA) for serum calcitonin (Ct).

METHODS: We collected 24 asymptomatic individuals from 8 unrelated Chinese families with MEN 2, and analyzed RET mutation and Ct levels. Then we performed TT on 17 of the 24 individuals, including TT (2/17), TT with bilateral level VI lymph-node dissection (B-LND(VI); 12/17) and TT with B-LND(VI) + modified unilateral/bilateral/local neck dissection (3/17).

RESULTS: Histopathology revealed bilateral/unilateral MTC in 15/17 (88.2%; median diameter, 1.0 cm) and bilateral C-cell hyperplasia in 2/17 (11.8%; p.V292M/R67H/R982C and p.C618Y). Lymph-node metastasis/fibro-adipose tissue invasion (p.C634R) or solely fibro-adipose tissue invasion (p.C634Y) were found in 2/17 (11.8%). Elevated pre-surgical Ct (pre-Ct) was identified by FACLIA in 17/17 (median age, 24.0), while pre-Ct by RIA was found in only 6/15 (P < 0.001). The median follow-up was 22.0 months, during which 16/17 had no abnormality (one p.C634R individual had elevated Ct), and another 7 carriers still had consistently undetectable Ct by FACLIA.

CONCLUSIONS: Our study highlights the importance and feasibility of individualized prophylactic TT for MEN 2-related MTC, based on predictive integrated screening of RET and pre-Ct levels. Besides, we recommend FACLIA to measure Ct for earlier diagnosis, treatment and follow-up monitoring of MTC.