99m Tc-Depreotide Scintigraphy in the Evaluation of Indeterminate Pulmonary Lesions: Clinical Experience

Indeterminate lung nodules (LN) constitute a clinical problem of increasing frequency that requires an effective diagnostic approach. This study evaluates the contribution of ^99mTc-depreotide scintigraphy in the management of such patients. Forty (40) patients (27 males/13 females) 29 to 82 years old (61 ± 12) with lung nodules/masses of indeterminate origin on computed tomography (CT) images were injected with ^99mTc-depreotide and underwent thoracic tomography (single photon emission computed tomography) 2 and 4-4.5 hours later. All parenchymal lesions (50) identified by CT were scored as negative or positive as to the uptake of ^99mTc-depreotide. Positive images were also evaluated semiquantitatively. Thirty (30) of 31 malignant lesions were positive (97% sensitivity) and 12 out of 19 benign lesions were negative (63% specificity), with positive images obtained in benign processes such as inflammation/infection and bronchiectasis. Semiquantitative analysis showed a statistically significant difference between benign and malignant positive lesions on the late images, and may play a complementary role in interpretation. ^99mTc-depreotide was a useful noninvasive tool in the evaluation of patients with LN, allowing for the exclusion of malignancy with great confidence, due to its high sensitivity. Because of moderate specificity, a positive test is best valued together with clinical and radiological features.