Objective: Our goal was to determine the role of technetium-99m hexakis-2-methoxyisobutyl isonitrile ((99m)Tc-MIBI) in the detection of neoplastic lung lesions.
Materials and methods: We prospectively studied 79 consecutive patients with indeterminate lung lesion between January 2006 and September 2007. All patients were submitted to (99m)Tc-MIBI single-photon emission chest tomography (SPECT) before invasive diagnostic procedure. Qualitative analysis was performed to evaluate SPECT images in order to localize abnormal activity in the radiologically demonstrated lesion. In addition, semiquantitative analysis was made by calculating tumor/contralateral normal lung ratio (T/N). Finally, the scintigraphic findings were correlated to the histopathological diagnosis obtained by invasive procedure or confirmation of instrumental exams.
Results: Sixty patients had a malignant lesion: 44 squamous cell carcinoma, 7 adenocarcinomas, 4 large cell carcinoma, 1 small cell lung cancer, and 4 metastases. The mean size+/-standard deviation of malignant nodules was 3.9+/-1.61 cm (range 1.5-5.5 cm). Nineteen patients had a benign disease. The mean size+/-standard deviation of benign nodules was 3.3+/-1.71 cm (range 2-6 cm). (99m)Tc-MIBI SPECT delineated focal lesions with an increase in tracer accumulation in 55/60 malignant lesions; in 5/60 malignant lesions was negative. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 91%, 73%, 91%, and 73%, respectively. In patients with neoplastic lesion, the mean T/N ratio value+/-standard deviation was 1.72+/-0.35 whereas in patients with benign lesions was 1.14+/-0.25. Semiquantitative analysis showed that for a T/N value >1.23, the value of sensitivity, specificity, PPV, and PNV were 91%, 84%, 94%, and 76%, respectively (ROC curve). Metastatic mediastinal lymph nodes were found in 3/57 patients. (99m)Tc-MIBI SPECT showed a specificity and PPV of 100% in the detection of mediastinal lymph nodes with sensitivity, and PNV of 66% and 97%, respectively. Age, sex, histological type, and size of lesion did not affect the SPECT results.
Conclusion: Our experiences seem to confirm that (99m)Tc-MIBI SPECT is a reliable diagnostic tool in the finding of lung cancer particularly cases in which radiological evaluation is indeterminate.