Diagnostic accuracy of contrast-enhanced computed tomography and positron emission tomography with 18-FDG in identifying malignant solitary pulmonary nodules.

Contrast-enhanced computed tomography (CECT) and positron emission tomography with 18-FDG (FDG-PET/CT) are used to identify malignant solitary pulmonary nodules. The aim of the study was to evaluate the accuracy of CECT and FDG-PET/CT in diagnosing the etiology of solitary pulmonary nodule (SPN). Eighty patients with newly diagnosed SPN >8 mm were enrolled. The patients were scheduled for either or both, CECT and FDG-PET/CT. The nature of SPN (malignant or benign) was determined either by its pathological examination or radiological criteria. In 71 patients, the etiology of SPN was established and these patients were included in the final analysis. The median SPN diameter in these patients was 13 mm (range 8-30 mm). Twenty-two nodules (31%) were malignant, whereas 49 nodules were benign. FDG-PET/CT was performed in 40 patients, and CECT in 39 subjects. Diagnostic accuracy of CECT was 0.58 (95% confidence interval [CI] 0.41-0.74). The optimal cutoff level discriminating between malignant and benign SPN was an enhancement value of 19 Hounsfield units, for which the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CECT were 100%, 37%, 32%, and 100%, respectively. Diagnostic accuracy of FDG-PET/CT reached 0.9 (95% CI 0.76-0.9). The optimal cutoff level for FDG-PET/CT was maximal standardized uptake value (SUV max) 2.1. At this point, the sensitivity, specificity, PPV, and NPV were 77%, 92%, 83%, and 89%, respectively. The diagnostic accuracy of FDG-PET/CT is higher than that of CECT. The advantage of CECT is its high sensitivity and negative predictive value.

What is currently the best radiopharmaceutical for the hybrid PET/CT detection of recurrent medullary thyroid carcinoma?

Among thyroid malignancies, medullary thyroid carcinoma (MTC) has some very specific features. Production and secretion of large amounts of peptides occur in malignant transformed C cells with few exceptions, leading to high serum levels of calcitonin (Ctn) and carcinoembryonic antigen (CEA), that act after thyroidectomy as tumour markers warning for the presence of persistent or metastatic MTC. The availability of those serum biomarkers with an excellent sensitivity challenges medical imaging to localise the recurrent cancer tissue, since surgery is a major therapeutic option. The aims of this article are (i) to review literature evidence about the efficacy and tolerance of radiopharmaceuticals for 3 targets of PET/CT imaging (glucose metabolism, bioamines metabolism and somatostatin receptors) and also bone scintigraphy which is recommended in the Guidelines of European Society for Medical Oncology (ESMO; (ii) to compare the availability and the costs in relation with those radiopharmaceuticals, (iii) and to discuss a possible sequence of those examinations, in order to optimise spending and to minimise the overall radiation dose. In this context of recurrent MTC suspected on rising tumour markers levels after thyroidectomy, this survey of literature confirms that FDOPA is the best radiopharmaceutical for PET/CT with significant diagnostic performance if Ctn>150 pg/mL; an early image acquisition starting during the first 15 min is advised. In negative cases, FDG should be the next PET radiopharmaceutical, in particular if Ctn and CEA levels are rapidly rising, and PET with a somatostatin analogue labelled with gallium-68 when neither FDOPA nor FDG PET are conclusive. Bone scintigraphy could complement FDG-PET/CT if FDOPA is not available.