Basal calcitonin needs the help of stimulation test for the diagnosis of sporadic medullary thyroid cancer (MTC) only in selected cases

Alessio Faranda; Alessandro Prete; Carla Gambale; Virginia Cappagli; Valeria Bottici; Eleonora Molinaro; Gabriele Materazzi; Rossella Elisei; Antonio Matrone

doi:10.1530/endoabs.101.PS2-13-02

PS2-13-02

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Endocrine Abstracts (2024) 101 PS2-13-02 | DOI: 10.1530/endoabs.101.PS2-13-02

ETA2024 Poster Presentations Medullary thyroid cancer-2 (10 abstracts)

Basal calcitonin needs the help of stimulation test for the diagnosis of sporadic medullary thyroid cancer (MTC) only in selected cases

Alessio Faranda ¹ , Alessandro Prete ² , Carla Gambale ² , Virginia Cappagli ² , Valeria Bottici ² , Eleonora Molinaro ² , Gabriele Materazzi ³ , Rossella Elisei ² & Antonio Matrone ²

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Author affiliations

¹Department of Clinical and Experimental Medicine, Unit of Endocrinology, University Hospital of Pisa, Department of Clinical and Experimental Medicine, Pisa, Italy; ²Department of Clinical and Experimental Medicine, Unit of Endocrinology, University Hospital of Pisa; ³Department of Surgical, Medical, Molecular and Critical Care Pathology, Endocrine Surgery Unit, University of Pisa, Pisa

Background: Calcitonin (CTN) is the main marker for the diagnosis and follow-up of patients with MTC. Its value, either basal (bCTN) or stimulated (sCTN) after calcium stimulation test (Ca-Test) is used in clinical practice for the diagnosis of patients with suspicious MTC. The aim of our study is to evaluate the performance of bCTN and sCTN in patients undergoing surgery with suspicion of sporadic MTC.

Methods: We evaluated 158 consecutive patients (Jan 2018-Oct 2023) with suspicious sporadic MTC who performed Ca-Test, having either bCTN and sCTN evaluated with the same assay (sensitive IMA) at the same laboratory, and subsequently treated by surgery.

Results: 57% were males, and the median age was 56.5 years (IQR 45-63). Histology was benign in 21 (13.3%), PTC in 28 (17.7%) of whom 21 with associated C-Cell Hyperplasia, MTC in 109 (69%) cases. The bCTN and sCTN values with improved sensitivity/specificity ratio for the diagnosis of MTC in the whole study group were 28.15 ng/l (AUC 0.907 - sens: 81.7%, spec: 89.8%) and 310.5 ng/l (AUC 0.809 - sens: 72.5%, spec 81.6%), respectively. In males these values were 33.2 ng/l (AUC 0.901 - sens 81.5%, spec 91.7%) and 341.5 ng/l (AUC 0.801 - sens: 74.1%, spec: 80.6%) while in females 22.1 ng/l (AUC 0.94 - sens: 87.3%, spec 92.3%) and 311.5 ng/l (AUC 0.897 - sens: 67.3%, spec: 100%). Seventeen out of 62 (32.2%) cases had an MTC in males and females with bCTN ≤ 33.2 and ≤ 22.1 ng/l, respectively. Of these, all were <1 cm, 88.2% N0 (11.8%, n = 2 were N1a, with micrometastases) and none had distant metastases. Conversely, only 4 patients did not have MTC if bCTN was > 33.2 ng/l in males and > 22.1 ng/l in females. In the 3 males, bCTN showed a median value of 40.2 ng/l while in the only female was 28.4 ng/l.

Conclusions: In our series, bCTN was more accurate than sCTN for the diagnosis of sporadic MTC. The values with better sensitivity and specificity were 33.2 ng/l and 22.1ng/l in males and females, respectively. MTCs diagnosed below these thresholds were all < 1 cm, with very few cases of CC lymph node micrometastases, without any distant metastatic case. Conversely, the few cases who did not have MTC having bCTN values slightly above the thresholds, could benefit of the Ca-Test.