Imaging of regional lymph node metastases with99mTc-depreotide in patients with lung cancer

The aim of this study was to evaluate the clinical usefulness of scintigraphy with99mTc-depreotide in the assessment of loco-regional nodal spread in patients with suspected lung cancer in comparison with computed tomography (CT). Eighty-six patients were investigated with single-photon emission computed tomography (SPECT) of the thorax after i.v. injection of 740 MBq99mTc-depreotide. The results were evaluated in conjunction with a thoracic CT scan in all 86 patients with 204 lymph node stations. The scintigraphic results were correlated with cytological (38), histological (20) or clinical-radiological (146) findings and compared with CT. The quantitative evaluation of depreotide uptake was performed on 48 cytologically or histologically verified nodal stations from 28 patients by SPECT using region of interest analysis with four different reference regions. 99mTc-depreotide scintigraphy for all 204 investigated lymph node stations had a sensitivity of 99% and a negative predictive value of 98% in determining lymph node involvement. Scintigraphy and CT showed the same level of accuracy, 76.4%. CT findings had a higher positive predictive value but a lower negative predictive value compared to 99mTc-depreotide scintigraphy. The quantitative evaluation of depreotide uptake in lymph nodes using vertebra as a reference region showed that a cut-off level of 0.56 excludes malignant involvement of lymph nodes, while a cut-off level of 1.66 excludes benign disease in lymph nodes. About 73% of all investigated lymph node stations showed uptake values between these cut-off levels. Absence of99mTc-depreotide uptake on scintigraphic imaging can exclude regional lymph node involvement with a high degree of probability and may be useful in clinical practice. The quantitative evaluation of depreotide uptake in regional lymph nodes did not increase the diagnostic accuracy of the method in general but did elucidate the lymph node status in some patients. (orig.)