Somatostatin receptor scintigraphy with ¹¹¹In-octreotide in pulmonary carcinoid tumours correlated with pathological and ¹⁸FDG PET/CT findings

Pulmonary carcinoid (PC) tumors are rare neoplasms of the lung with good prognosis but diagnosis may be demanding since there is no exclusive modality alone to clearly differentiate a PC tumor. The purpose of this study is to establish the diagnostic features of somatostatin receptor scintigraphy (SRS), comparatively (where available) with ¹⁸FDG PET/CT (PET/CT) correlated with histopathologic findings.

Twenty-one patients who underwent SRS with ¹¹¹In-octreotide and were diagnosed as having PC tumors were retrospectively studied. Thirteen patients were performed PET/CT. Primary tumour size, Ki-67 indexes, image analysis data of SRS and PET/CT including maximum standardized uptake values (SUVmax) together with false negative, false positive, true positive and true negative lesions were documented and discussed.

Eleven (52.4 %) patients were typical (TC) and 10 (47.6 %) were atypical carcinoids (AC) with mean Ki-67 indexes of 2.1 and 24 %, respectively. Patients underwent SRS for solitary pulmonary nodule (SPN) characterization (n = 12) and determination of disease extension (n = 9). Overall sensitivity and specificity of SRS in the detection of primary tumour, lymph nodes (LN) and distant metastasis (DM) were 76 and 97 %, respectively, whereas, positive and negative predictive values were 95 and 86 %. PET/CT was performed for determining disease spread (n = 3) and metabolic characterization (n = 10) of SPNs. Mean SUVmax in the primary pulmonary lesion in TCs and ACs were 2.9 ± 0.8 and 7.9 ± 5.4, respectively. Nodal involvement (n = 5) and DM (n = 3) were also detected. Sensitivity and specificity of PET/CT in the detection of primary tumour, LNs and DM were 85 and 89.4 %, respectively.

SRS is useful in the diagnosis and monitoring of PC tumors when incorporated with ¹⁸FDG PET/CT as a primary staging tool particularly in the determination of disease spread.