The Value of HRCT and Tc-Depreotide in the Evaluation of Pulmonary Lesions

Lung cancer is one of the most common cancers worldwide, and the overall incidence continues to increase. Despite advances in treatment, the overall 5-year survival is still approximately 10% to 15%. A better therapeutic impact depends on the ability to diagnose the cancer in an early stage. When the suspicion of lung cancer is raised, a computed tomographic (CT) scan is necessary. A number of screening studies of lung cancer have been published.1–4 In these studies, the sub-centimeter, non-calcified lesions were identified in 30% to 60% of cases. However, only 1% to 3 % of these lesions turned out to be malignant. Thus, the final diagnosis can not rely on CT alone; invasive procedures are needed. Imaging-guided fine-needle aspirations have an overall accuracy of 64% to 100% for detecting malignancy,5,6 and bronchoscopy-guided biopsies of centrally located lesions have an accuracy of 70% to 90%.7 Follow-up CT is therefore still needed in a number of patients. Recently, new techniques for detecting lung cancer have become available. It seems that refinement of the CT technique with high-resolution CT (HRCT) in subgroups of lesions increases the specificity solely by morphological characterization, thereby reducing the need for invasive procedures.8,9 Thus, Furuya et al.8 found an accuracy for malignancy of more than 93% by using specific morphologic criteria on HRCT. Nuclear medicine methods have also emerged. The high level of somatostatin receptor expression on various tumor cells has provided the molecular basis for the successful use of radiolabeled somatostatin analogs as tumor tracers. Somatostatin-receptor scintigraphy is a well documented method of diagnosing neuroendocrine tumors10 and has been used since 1989. Furthermore, it has been shown to be able to detect both small cell lung cancer (SCLC), which possesses neuroendocrine characteristics, as well as non-small cell lung cancer (NSCLC).11 Until recently, an Indium-labeled somatostatin analogue, octreotide, was the only tracer used for imaging. However, in 2000, a Tc-labeled somatostatin analogue depreotide became commercially available for scintigraphic imaging of suspected malignant tumors in the lung. So far, studies have found that Tc-depreotide has a high sensitivity for detecting lung cancer (89% to 100 %) but low specificity (43% to 73%).12–19 F-fluoro-2-deoxy-D-glukose (FDG) positron emission tomography (PET) has an integral role in the management of many oncological tumors, including lung tumors, in regard to characterization and staging.20 However, compared with single emission computerized tomography (SPECT) scanners, PET scanners are still more costly, and availability is still rather limited, even in developed countries. The aim of this study was to assess the diagnostic impact of HRCT and Tc-depreotide separately and in combination among patients with pulmonary lesions demonstrated by conventional CT.