Purpose: Sentinel node biopsy (SNB) is a surgical technique for detecting micrometastatic disease in the regional draining nodes. 2-fluorine-18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) scanning is an imaging technique that can detect clinically undetectable metastases. This prospective study was undertaken to compare the sensitivity of FDG-PET scanning with SNB in the detection of micromatastatic malignant melanoma.
Patients and methods: Fifty consecutive patients (23 women, 27 men; mean age, 53 years) with primary melanoma >1 mm thick or lymphatic invasion were recruited (mean, 2.41 mm). Primary lesions had been narrowly excised (<1 cm). Patients underwent PET scanning followed by SNB, using a dual technique. Preoperative lymphoscintigraphy was used to identify the draining basin. Lymph nodes were examined histologically and immunostained for S100 and HMB 45.
Results: The sentinel node (SN) was identified in all patients. Fourteen patients (28%) had positive SNBs, including eight patients with melanoma <1.5 mm thick. In none of these 14 patients did PET scans identify metastatic disease in the SN or draining basin. In seven patients, the PET scans were positive in other locations, and in four cases, this was suspicious of metastatic disease. However, no patient has developed recurrent melanoma (mean follow-up, 15 months). All patients with positive SNBs underwent therapeutic lymph node dissection. Further lymph node involvement was found in two patients (primary lesions, 1.3 mm and 3.5 mm thick).
Conclusion: This study demonstrates the limitations of FDG-PET scanning in staging patients with primary melanoma. SNB is the only reliable method for identifying micrometastatic disease in the regional draining node.