Staging of regional lymph nodes in melanoma patients by means of 99mTc-MIBI scintigraphy

Most first relapses in patients with melanoma occur in regional lymph node basins. Such lesions are frequently diagnosed clinically during the first 2 y of follow-up. In the last few years, our group has been studying the usefulness of Tc-99m-methoxyisobutylisonitrile (MIBI) scintigraphy in the evaluation of recurrent melanoma lesions. The aim of the present study was to prospectively evaluate the clinical value of Tc-99m-MIBI scintigraphy in the diagnosis of subclinical nodal metastases. Methods: We included 66 patients within 3 mo of melanoma diagnosis, with Breslow thickness > 1.0 mm, all treated with wide local excision of the primary lesion. When Tc-99m-MIBI scanning was performed, 49 of them did not have evidence of nodal disease, and 17 had clinically questionable regional lymph node lesions. Planar images of lymph node regions were acquired 10 min after injection, using a dose of 740-1,110 MBq and a large-field-of-view gamma camera equipped with a low-energy high-resolution collimator. Scan findings were confirmed by pathology or by clinical follow-up (median, 35 mo). Results: Thirty of 33 patients with regional lymph node metastases received a correct diagnosis, 14 with palpable lesions and 16 wit nonpalpable lesions. In 3 cases that were initially Tc-99m-MIBI negative, nodal metastases were found during follow-up. The following diagnostic values were calculated: sensitivity, 0.91 (95% confidence interval [CI], 0.75-0.98); specificity, 0.85 (95% Cl, 0.67-0.94); likelihood ratio of a positive test, 6.0 (95% CI, 2.7-13.5); and likelihood ratio of a negative test, 0.11 (95% CI, 0.036-0.32). Conclusion: Tc-99m-MIBI scanning may have a secondary role in the staging of regional lymph nodes in patients with clinically localized melanoma who are not good candidates for sentinel node biopsy.