An increase in basal and Pentagastrin (Pg) stimulated calcitonin (CT) concentration is a specific feature of medullary thyroid carcinoma (MTC). Routine basal CT measurement in nodular thyroid diseases is controversial. Pg stimulation is expected to increase the basal CT specificity in MTC screening, although false positive responses in patients without MTC have been reported.
Aim: To report the diagnostic accuracy of Pg-stimulated CT in surgically treated patients with nodular thyroid diseases and basal CT in the high-normal range or slightly supranormal (<42 pg/ml).
Patients and methods: We studied 12 pts (11 M, 1 F, aged 55.7±24.1), without evidence of MTC at pathological examination (nonMTC-group) and 9 pts (1 M, 8 F, aged 37.1±26.3) with pathologically proven MTC (hereditary in 6 cases) (MTC-group). Tumor size in MTC-group was comparable in hereditary and non-hereditary cases (P=0.129). Serum CT was measured (Immulite 2000 Calcitonin, Medical Systems, normal values 015 pg/ml) in basal condition and 1, 2, 4 and 10 min after i.v. injection of Pg (0.5 mcg/kg). ROC curve was performed by MedCalc-package.
Results: Mean basal and Pg-stimulated CT concentrations were 20.6±8.1 (range 10.239) and 119.5±77.7 (range 21281) in nonMTC-group and 28.6±8.9 (range 13.441.5) and 685.7±593 (range 1161600) in MTC-group. In nonMTC-group, Pg-stimulated CT levels were higher in cases with pathological evidence of C-cell-hyperplasia (CCH) than in cases without CCH (172.3±69.2 vs 66.7±42.5, P<0.05).
At ROC-analysis a Pg-stimulated CT value>193 pg/ml showed the best accuracy in detecting MTC with 77.8% sensitivity, 92.9% specificity; positive and negative likelihood ratios were 87.5 and 84.6%.
Conclusions: On considering the large orverlap of PG-stimulated CT in patients with and without MTC, any cut-off value chosen as a criterium to recommend surgery in patients with nodular thyroid disease remains fallible and possibly bound to change over time.
03 - 07 May 2008
European Society of Endocrinology