Technetium Tc-99M Depreotide

Background: Somatostatin receptor (SSTR) scintigraphy with 99mTc-depreotide is used for differential diagnosis of solitary pulmonary nodules. The method is based on SSTR expression in cancer tissue. Purpose: To estimate the expression of SSTRs in non-small-cell lung cancer (NSCLC) in vitro, and to determine the correlation between 99mTc-depreotide uptake in vivo and different tumor characteristics determined in vitro, such as tumor grade, and presence of SSTR2, MIB-1, and p53. Material and Methods: A total of 127 patients with lung lesions detected on computed tomography (CT) were investigated with SSTR scintigraphy after injection of 740 MBq 99mTc-depreotide. This study includes 19 patients with NSCLC with histologically proven diagnosis. The quantitative evaluation of 99mTc-depreotide was performed using region-of-interest analysis and includes tumor counts/cm3, background counts/cm3, and the ratio between tumor and background counts. Results: 99mTc-depreotide uptake was found in all NSCLC tumors, which expressed SSTR2 defined in vitro by immunochemical methods. SSTR2 expression was negatively correlated to the degree of the tumor's differentiation ( P<0.05). 99mTc-depreotide uptake in tumor cells did not correlate with tumor grade, or SSTR2, MIB-1, or p53 expression. Conclusion: There is an expression of SSTRs in NSCLC. The degree of tumor differentiation correlates negatively with SSTR2 measured in vitro and positively with MIB-1 expression in tumor tissue. No correlation was found between 99mTc-depreotide uptake and possible prognostic factors such as MIB-1 and p53 expression in tumor cells in NSCLC. Lastly, no correlation was found between 99mTc-depreotide uptake and tumor grade or SSTR2 expression.

Background: In Sweden, there are over 3000 new lung cancer cases every year. There are still numerous patients with undetermined lesions after routine diagnostic evaluation by clinical examination, chest radiography, computed tomography (CT) of the thorax, and bronchoscopy. An appropriate method for further diagnostic workup is therefore needed. Purpose: To evaluate the diagnostic value of the somatostatin analogue depreotide in patients with suspected lung cancer, and to determine in which clinical settings it would be beneficial to use 99mTc-depreotide scintigraphy. Material and Methods: We included 99 consecutive patients referred to our hospital with suspected lung cancer. A clinical examination, bronchoscopy, chest radiography, CT of the thorax and upper abdomen, and scintigraphy were done. Scintigraphy was performed after injection of 740 MBq 99mTc depreotide with tomographical imaging of the thorax and whole-body scanning. The diagnostic outcome of the scintigrams was compared to CT, using morphology or clinical outcome as the endpoint. Results:99mTc-depreotide uptake was found in 62 out of 66 malignancies, including 57 of 58 primary lung cancer cases. Two cases of lung metastasis (one from a colon cancer and one from an adenoid cystic carcinoma originating in the palate) and one rib chondrosarcoma did not show depreotide uptake. There were 33 patients with benign lesions, of whom 16 displayed false-positive 99mTc-depreotide uptake, whereof 11 were pneumonias. Tc-99m-depreotide uptake was absent in 17 patients with benign lesions, including all 10 hamartomas. The sensitivity in detecting malignancy was 94%, and in detecting lung cancer 98%. The specificity was calculated based on two sets of data. When all cases were used, the specificity was 52%. If the 12 pneumonias are excluded, the specificity was 77%. Conclusion:99mTc-depreotide scintigraphy has a high sensitivity in detecting lung cancer. The method is useful in decision-making with respect to surgery.