Diagnostic imaging of typical lung carcinoids: relationship between MDCT, 111In-Octreoscan and 18F-FDG-PET imaging features with Ki-67 index

Aims: This study analyses the capability of contrast-enhanced multi-detector computed tomography (MDCT) and spectrum of molecular imaging to characterize typical carcinoids (TCs) of lung and their relationship with Ki-67 index. Materials and methods: We analysed 68 patients with histological diagnosis of pulmonary TC, which underwent both MDCT and nuclear molecular imaging (somatostatin receptor scintigraphy/SPECT with 111In-pentetreotide and 18F-FDG-PET/CT) at staging evaluation before surgery. The MDCT scan was reviewed for the following features: size, margins, contrast enhancement, presence of calcifications, bronchial obstruction, lymph nodes and metastases. In 111In-pentetreotide SPECT, tumour/non-tumour ratio was measured at 4- and 24-h post-injection and the per cent difference was calculated (T/NT%). FDG uptake was measured as the ratio between lesion SUVmax and liver SUVmean (SUV ratio). All imaging features were correlated between them and with Ki-67 index. Results: Forty-four of the 68 lesions (65%) were in the right lung. In MDCT, scan lesions appeared as a well-defined nodule in 44 patients (65%) and irregular mass in 24 patients (35%). Contrast intense enhancement was present in 53 patients (78%), calcifications in 20 patients (29%) and bronchial obstruction in 24 patients (35%). Lymph nodes and metastasis were present in 13 (19%) and 15 (22%) patients. Ki-67 index was negatively correlated with T/NT% and positively with SUV ratio; T/NT% and SUV ratio were inversely correlated. The presence of irregular margins and metastases was negatively related to T/NT%. The presence of a mass, irregular margins, bronchial obstruction, lymph nodes and metastasis was positively related to higher SUV ratio. The presence of irregular margins, bronchial obstruction, lymph nodes and metastases was significantly correlated with a higher grade of Ki-67 index. Conclusions: MDCT and nuclear molecular imaging are important to characterize lung TCs. The majority of TCs appear as a well-defined nodule generally not associated with extra-thorax signs. We found a significant correlation between some MDCT aspects, nuclear medicine features and Ki-67 index. The association of MDCT and nuclear medicine imaging may be useful in predicting proliferative activity and prognosis of lung TCs.