BackgroundProcalcitonin (proCt) was recently proposed as an alternative or in addition to calcitonin (Ct) in medullary thyroid cancer (MTC) diagnostics.MethodsSerum basal Ct (bCt) and proCt (bproCt) levels were measured before surgery from a consecutive series of patients with (n=43) and without (n=75) MTC, retrospectively collected in Padua. Serum bproCt, bCt and stimulated proCt and Ct (sproCt and sCt) were measured in another consecutive series of 33 patients seen at three tertiary-level institutions undergoing a calcium stimulation test prior to surgery, 20 of them with a final diagnosis of MTC, and 13 with non-MTC nodular disease.ResultsMedian bproCt levels were higher in MTC than in non-MTC. A positive correlation was found for bproCt with bCt (P<0.01, R2 = 0.75), and with tumor size (P<0.01, R2 = 0.39). The cut-off for bproCt differentiating between MTC and non-MTC patients was >0.07 ng/ml (sensitivity: 85.7%, specificity: 98.9%, positive predictive value [PPV]: 98.2%, negative predictive value [NPV]: 90.6%, P<0.01). While bproCt was >0.07 ng/ml in 38/39 (97.4%) patients with MTC >10 mm, it was above said cut-off only in 15/23 (65.2%) patients with tumors ≤10 mm. A sproCt >0.19 ng/ml was able to identify MTC [sensitivity: 90.0%, specificity:100.0%, PPV: 100.0%, NPV: 86.7% (P<0.01)].ConclusionsOur data suggest that bproCt can be a good adjunct to Ct for MTC diagnostic purposes. In consideration of its high specificity, it can be used in combination with Ct in MTC diagnostics, particularly in the case of mildly elevated basal Ct levels.

Objective: Calcitonin (Ct) represents the most important biochemical marker of medullary thyroid cancer (MTC), but has certain limits. We analysed the performance of Procalcitonin (ProCt) in follow-up MTC patients. Methods: in this monocentric and retrospective study we consecutively obtained ProCt and Ct values from all MTC patients that we visited during the period from April 2021 to May 2022. Patients were defined as having a structural evidence of disease (29/90, 32.2%) irrespective of Ct values or, in its absence, as not evident disease (NED) if Ct was ≤10 ng/L (47/90, 52.2%), or minimal residual disease, if Ct was >10 ng/L (14/90, 15.6%). Results: Ct and ProCt values were highly correlated (r=0.883, P<0.01). Median ProCt values differed between NED, minimal residual disease and structural disease, being 0.04 ng/ml, 0.26 ng/ and 1.98 ng/ml, respectively (P<0.01). ProCt was undetectable (<0.04 ng/ml) in 40/47 (85.1%) of NED patients, in 3/14 (21.4%) patients with a minimal residual disease and in none of the patients with a structural disease (P<0.01). Among the 11 patients with detectable but ≤10 ng/L Ct and undetectable ProCt values, none had a structural disease. The most accurate cut-off of ProCt to distinguish between presence or absence of a structural disease was >0.12 ng/ml (P<0.01, AUC: 0.963), with the following sensitivity, specificity, positive predictive value and negative predictive value (NPV): 100%, 83.61%, 74.4% and 100.0%. Conclusions: ProCt and Ct have a high correlation in MTC follow-up. ProCt may be useful as an adjunct to Ct especially for its NPV concerning structural disease.

Background: procalcitonin (proCt) was recently proposed as an alternative or in addition to calcitonin (Ct) in medullary thyroid cancer (MTC) diagnostics. Methods: serum basal Ct (bCt) and proCt (bproCt) levels were measured before surgery from a consecutive series of patients with (n=43) and without (n=75) MTC, retrospectively collected in Padua. Serum bproCt, bCt and stimulated proCt and Ct (sproCt and sCt) were measured in another consecutive series of 33 patients seen at three tertiary-level institutions underwent a calcium stimulation test prior to surgery, 20 of them with a final diagnosis of MTC, and 13 with non-MTC nodular disease. Results: median bproCt levels were higher in MTC than in non-MTC. A positive correlation was found for bproCt with bCt (P<0.01, R2=0.75), and with tumor size (P<0.01, R2=0.39). The cut-off for bproCt differentiating between MTC and non-MTC patients was >0.07 ng/ml (sensitivity: 85.7%, specificity: 98.9%, positive predictive value [PPV]: 98.2%, negative predictive value [NPV]: 90.6%, P<0.01). While bproCt was >0.07 ng/ml in 38/39 (97.4%) patients with MTC >10 mm, it was only above said cut-off in 15/23 (65.2%) patients with tumors ≤10 mm. A sproCt >0.19 ng/ml was able to identify MTC (sensitivity: 90.0%, specificity:100.0%, PPV: 100.0%, NPV: 86.7% [P<0.01]). Conclusions: proCt cannot replace Ct as the standard of care in the MTC diagnosis, because it often fails to identify a small MTC. That said, it has a very high specificity and can be used in combination with Ct in MTC diagnostics, particularly in the case of mildly elevated basal Ct levels.