The solitary pulmonary nodule - malignant or benign?

A new study published in the journal Respiration shows good overall diagnostic accuracy of technetium-99m (99mTc)-depreotide single photon emission computed tomography (SPECT) in separating malignant from benign solitary pulmonary nodules (SPNs) of indeterminate origin.

99mTc-depreotide is a low-cost radionuclide easy to obtain and to image in routine clinical conditions.

The primary objective of this first large, open-label, multicentre study of 99mTc-depreotide in Europe was to assess its diagnostic performances and compare it with fluor-18-fluoro-deoxyglucose positron emission tomography (FDG-PET), which has also been demonstrated to be efficient in the characterization of SPNs. However, PET cameras are only available in large centres.

One hundred and eighteen patients presenting with an SPN of 3 cm or smaller suspected of malignancy on CT were included in this trial. The SPECT images were acquired 1.1-4.5 h after injection of 459-770 MBq of 99mTc-depreotide. A subset of 29 patients also underwent FDG-PET imaging. The images were interpreted blindly and correlated with histopathology. 99mTc-depreotide SPECT was positive in 65 of 73 patients with a malignant lesion and negative in 30 of 45 patients with a benign lesion, resulting in a sensitivity, specificity and diagnostic accuracy of 89, 67 and 81%, respectively. In 40 patients with an SPN of 1.5 cm or smaller, the diagnostic accuracy was 88, sensitivity 75 and specificity 96%. In the subset of 29 patients who underwent both 99mTc-depreotide SPECT and FDG-PET imaging, sensitivity, specificity and diagnostic accuracy were identical for both modalities, i.e. 90, 67 and 83%, respectively.

This study confirms a satisfying performance of 99mTc-depreotide in separating malignant and benign SPNs. Since access to FDG-PET remains limited, 99mTc-depreotide is advantageous as it can be imaged with traditional nuclear medicine equipment.

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