Calcium stimulation test for the rare mutation carriers of RET

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 414-428-Thyroid Neoplasia & Case Reports
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-425
Maiko Kakita*1, Youhei Ueda1, Kanako Nakao1, Takeshi Usui1, Rieko Nakatani1, Sachiko Tsukamoto Kawashima1, Kazutaka Nanba1, Mika Tsuiki1, Tetsuya Tagami1, Mitsuhide Naruse1, Yoshiki Watanabe2, Yusuke Mori2, Ryo Asato2, Tetsuro Yamamoto2 and Akira Shimatsu1
1National Hospital Organization Kyoto Medical Center, Kyoto, Japan, 2National Hospital Organization Kyoto Medical Center
Background : Multiple endocrine neoplasia (MEN) type 2 and familial medullary thyroid carcinoma (FMTC) are autosomal dominant inherited diseases caused by genetic mutations of the RET-proto-oncogene. Genetic testing of RET provide a critical information on the prophylactic surgery for medullary thyroid carcinoma (MTC) in mutation carriers. Prophylactic total thyroidectomy depending on mutation-based risk levels is recommended in the various countries including US, however, is not generally done in Japan. Calcitonin (CT) is a very sensitive bio-marker of MTC, and measurement of CT stimulated with intravenous calcium (Ca) gluconate has been widely adapted. However, standard values for this test have not been reported. And then, there is very few report of Ca stimulation test using the same measuring assay as our country.

Objective : The natural history of some rare and low risk type of RET mutation carriers is not fully understood. Therefore, prophylactic thyroidectomy might be debatable in such cases. The aim of this study is to evaluate whether Ca stimulation test can detect the early stage of C cell lesions in these rare RET mutation carriers.

Patients : Four rare RET mutation carriers (V804M in case 1, Q781R in case 2 and 3, and E768D in case 4) were subjected for Ca stimulation test (Ca gluconate 2mg/kg/min).

Results : In all cases, basal serum CT and CEA levels were within normal ranges, and ultrasonography showed no solid mass in their thyroid glands. Neither parathyroid glands nor adrenal glands showed detectable mass in the imaging studies. Two of the four cases (case 1 and case 2) showed an increase of the CT levels after Ca infusion. The basal/peak CT levels of case 1 and case 2 were 40(normal range;15-86)/161 pg/ml, and 22/116 pg/ml, respectively. On the other hand, no CT increase was observed in case 3 and case 4. Total thyroidectomy was underwent for case 1, and C cell hyperplasia had been pathologically identified.

Conclusions : The Ca stimulation test was done for four cases of rare RET mutation carriers. C cell hyperplasia was demonstrated in one case, which showed CT increase after Ca stimulation. Although further study will be needed, Ca stimulation test may provide useful information on rare RET mutation carriers about the suitable timing of surgical management. However, cut-off level of CT level in various assay kits should be studied.

Nothing to Disclose: MK, YU, KN, TU, RN, STK, KN, MT, TT, MN, YW, YM, RA, TY, AS

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