Endocrine Abstracts

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor occurring either sporadically or in a hereditary form that can be cured by complete resection of the tumor and any locoregional metastases, but appropriate treatment remains less clear in patients with residual or recurrent disease. Herein we report the case of a 51-year-old man that was diagnosed with bifocal right-sided medullary thyroid cancer in October 2021 after a fine needle aspiration suggestive of an MTC. The patient underwent the following 3 operations within 2 years: a total thyroidectomy (10/2021), a right central and lateral neck dissection (2/2022), and a right central neck dissection plus right mediastinal lymphadenectomy (7/2022). The histology of the primary operation revealed 2 foci of MTC (max. diameter 4 cm and 1,1 cm) in the right lobe with extrathyroidal extension and 4 infiltrated lymph nodes out of 4 together with an intrathyroidal 0.4 cm large papillary thyroid carcinoma in the left lobe. The histology of the second and third operation revealed five infiltrated lymph nodes out of sixteen, and seven infiltrated lymph nodes out of seven respectively. RET mutation analysis was negative. Calcitonin levels were measured only one month postoperatively when he presented in our clinic and were as high as 3360pg/ml and dropped to 1259pg/ml, and 277pg/ml after the first, second and third operation respectively. After the first operation, in the ¹⁸F-FDG PET/CT increased uptake was documented in several lymph nodes of the right upper paratracheal space and anterior upper mediastinum, with respective correlate in the cervical MRI. The ⁶⁸Ga-DOTATOC PET/CT performed after the second operation documented increased uptake in the right paratracheal region and in the anterior upper mediastinum. In view of the positive ⁶⁸Ga-DOTATOC, the revision of the histology demonstrated positive expression of somatostatin receptor (SSTR)2 and SSTR5 (score 3 and 2, according to Volante respectively) and ki-67 3%. A first-generation somatostatin analogue (SSA) treatment was decided with monthly Octreotide LAR 30 mg since an increase of calcitonin to 371pg/ml was observed. Six months later, and as the calcitonin levels did not respond adequately to the treatment (an initial drop of calcitonin levels to from 314pg/ml was followed by an increase to 490 pg/ml). Then medical therapy with monthly Pasireotide LAR 60 mg was initiated and 5 months later (10/2023) the calcitonin levels dropped at 261pg/ml. An antidiabetic therapy was also initiated, probably as side effect of the drug. Somatostatin analogues treatment seems to be a rationale alternative in patients suffering from recurrent and residual sporadic RET-negative medullary thyroid cancer when there is evidence of SSTRs presence by their positive immunohistochemical expression in the tissue and/or by the increased uptake in ⁶⁸Ga-DOTATOC PET/CT.