Usefulness of receptor scintigraphy using 99mTc-EDDA/HYNIC-TOC in differential diagnostics of solitary pulmonary nodules

Full text: At present two diagnostic methods are considered effective to differentiate malignant and benign solitary pulmonary nodules (SPNs): PET study using 18-fluordeoxyglucose (18FDG) and a receptor scintigraphy using 99mTc-depreotide, a somatostatin analogue labelled with technetium-99m. However, the former technique is very expensive and therefore not widely available and the latter, although less expensive, is far from wide use. Recently, numerous communications appeared on new somatostatin analogues labelled with radionuclides, potentially useful in oncological diagnostics. The aim of the work was to examine the usefulness of 99mTc-EDDA/HYNIC-Tyr3-octreotide, a technetium99mlabelled somatostatin analogue produced in Poland by Radioisotope Center POLATOM, in differential diagnostics of SPNs. 38 patients (21 males and 17 females at age between 30 and 76 years; mean age 51) with SPNs were evaluated. 26 patients with malignant tumours had the following etiologies: 8 adenocarcinomas, 4 squamous cell lung cancers, 2 small cell lung cancers-SCLC, 2 large cell carcinomas, 5 non-small cell lung cancers-NSCLC, 1 liposarcoma, 2 carcinoids, 1 leiomyosarcoma-metastasis and 1 malignant melanoma-metastasis. The remaining 12 patients had benign tumours: 5 tuberculomas, 3 other granulomas, 2 non-specific inflammatory infiltrates and 2 hamartomas. Administered activity ranged between 740 and 925 MBq (corresponding to about 20 μg of HYNIC-TOC). SPET acquisition with the following parameters was done: collimator HI-RES, image matrix: 128x128, time/frame: 25s. Acquisition started 2 h post injection. During tomographic reconstruction Metz filter of power 3 and a FWHM of 1.0 cm was applied. Images were evaluated visually: 3 series of slices (transverse, sagittal and coronal) were inspected to see whether a lesion of enhanced uptake of activity could be observed at a location corresponding to the nodule on the radiogram. Verification of scintigraphic results was based upon pathological examination of tumour samples (histopathology or cytology). In some patients verification was additionally based on bacteriology and clinical history of disease. Scintigrams were positive in 23 out of 26 (88%) malignant nodules, including all cases of primary lung cancer, small cell and non-small cell. False negative results were in cases of metastatic tumours (melanoma and leiomyosarcoma) and a small carcinoid (tumour diameter - 8 mm). Scintigrams were negative in 11 out of 12 (92%) benign tumours, excepting one tuberculoma. In conclusion, 99mTc-EDDA/HYNIC-TOC is a promising radiopharmaceutical for effective scintigraphic differentiation between malignant and benign SPNs. It may widen availability of radionuclide differential diagnostics of SPNs. (author)