Аpplication of the hybrid imaging techniques SPECT/CT and PET/CT in the diagnostic algorithm in patients with somatostatine expressing neuroendocrine tumors
I. Kostadinova, D. Zlatareva, V. Stoinova, J. Mihailova, Sv. Dineva, М. Garcheva, V. Groudeva
|Somatostatin receptor scintigraphy (SRS) is known to be highly sensitive for diagnosis of primary carcinoid tumors, regional lymph nodes’ and distant metastasis. In many cases the examination which reflects the early functional changes is performing superior to CT and MRI. The aim of our study was to show our experience in the application of the hybrid imaging techniques SPECT/CT and PET/CT in the diagnostic algorithm of patients with a proven somatostatine expressing tumors with unknown primary, for staging, localization and evaluation of the therapy. In total 57 patients were investigated, using the new somatostatine analog 99mTc-HYNIC-TOC (Tektrotyd,PL) at activity between 370-550 MBq. The average level of chromogranine was 196 ng/ml and that of Ki 67-26%. Whole body and SPECT/CT scintigraphy were performed 2- 4h p.i. In 17/57 of the patients, in whom Ki 67 was above 2% and tumor localization and/ or stage still unclear after the examination, PET/CT (using an average 370 MBq 18FFDG) was additionally applied within one week. The SRS was true positive in 37/57 of the patients, true negative in 15/57, false negative in 3/57 and in 2/57-false positive, with a sensitivity of 92.5%, specificity 88.2% and accuracy 91.2%. PET/CT was positive in all investigated 17 patients with more aggressive behavior and helped for localizing of the primary tumor. All patients with positive scintigraphies were referred for surgery or somatostatine therapy and/or chemotherapy depending on the stage and the differentiation of the disease. In summary, we suggest that SRS, using the new 99mTc-HYNIC-TOC and SPECT/CT technique are very reliable in patients with unknown primary from NET, for staging, for the choice and for follow up the effect of therapy. The therapeutic strategy could be optimized additionally applying 18F-FDG PET/CT in some of the patients.
Key words: SPECT/CT. PET/CT. DIAGNOSTIC ALGORITHM. SOMATOSTATIN EXPRESSING NEUROENDOCRINE TUMOR