Endocrine Abstracts (2018) 55 WD6 | DOI: 10.1530/endoabs.55.WD6

Advanced medullary thyroid cancer with metastatic disease at diagnostic in young patient negative for RET mutation- to treat or not to treat with tyrosine-kinase inhibitors

Mariana Costache Outas1 & Cosmin Giulea2,3

1Coltea Clinical Hospital, Bucharest, Romania; 2‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania; 3Elias University Emergency Hospital, Bucharest, Romania.

We report a 21-year-old man who referred to endocrinologist following biopsy of a left-sided cervical mass. The pathological examination was diagnostic for medullary thyroid carcinoma (MTC). Physical examination was remarkable for a firm 3-cm nodule in right thyroid lobe and another 3 cm. firm nontender mass in left thyroid lobe. The calcitonin was 15,324 pg/ml, and carcinoembryonic antigen was 415 ng/ml. The calcium level was 10.3 mg/dl (<10 mg/dl) with unsuppressed parathormone of 37.1 pg/ml (15–65) and negative screening for pheochromocytoma. The ultrasound of the cervical region shows both thyroid lobes occupied by hypoechoic irregular masses with macrocalcifications and blood flow and metastatic bilateral adenopathies. The tomography of the chest revealed multiple bilateral nodular lesions (maximum 10 mm.) suggestive of pulmonary metastasis. The tomography of abdomen described hepatic lesions (>20) of sizes up to 22/17 mm. The patient was negative for germline RET mutations. The total thyroidectomy with central and cervical compartment dissection was carried out by a thyroid surgeon, as well as the exclusion of three out of four parathyroid glands. The patient received thyroid substitution therapy and active vitamin D supplement. A nadir for calcitonin of 16,646 pg/ml was registered three months following surgery. The follow up with repetitive tumor markers, and evaluation of tumors showed a slow progressive increase of calcitonin of 21.55% in 0.83 years (52% increase in 24 months) with the stable size of the pulmonary and hepatic metastasis and no tumor tissue in the cervical region.

Discussion: The study by Wells establishes the efficacy of Vandetanib in patients with locally advanced or metastatic MTC. This study included 15% patients that the progression of the disease was not documented before entry. The response rate to Vandetanib with sporadic MTC seems to correlate with RET mutations with better responsive rate (54.5%) when the mutation is present compared with the 32% in the patients who were negative for mutations (or have unknown mutation status). The relatively indolent tempo of disease in some patients with MTC makes the risk: benefit ratio of treatment unfavorable in patients with a low disease burden who experience slow progression and surviving rates of 100% at ten years when the doubling time of calcitonin is more than 24 months. In contrast, patients who are symptomatic, have a high disease burden or have rapidly progressing disease stand to benefit the most from treatment with Vandetanib.

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