Study: FDG PET bests CT in detecting lymph node metastatic sites

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FDG PET and CT are equivalent in upstaging patients with melanoma; however, FDG PET detected more metastatic sites, especially bone and subcutaneous, according to a study in the Oct. 1 issue of the Journal of Clinical Oncology.

Patients with melanoma and potentially resectable lymph node metastases require accurate staging to prevent unnecessary surgery. FDG PET is attractive for this because melanoma typically is FDG avid, according to the authors.

Esther Bastiaannet, MSc, from the departments of surgical oncology, radiology, nuclear medicine and molecular imaging at the University Medical Centre Groningen, the Netherlands, and colleagues said the aim of this prospective multicenter study was to perform a head-to-head comparison of FDG PET and CT in staging of patients with melanoma with palpable lymph node metastases in terms of diagnostic accuracy and impact on treatment.

The investigators included all consecutive patients with palpable, proven lymph node metastases of melanoma between mid 2003 and 2007. They recorded the number/site of distant metastases detected with FDG PET and CT. Histology/cytology or six months follow up were the reference standard.

According to the authors, distant metastases were suspected by FDG PET in 32 percent of the 251 patients and by CT in 29 percent. They reported that upstaging was correct in 27 percent by FDG PET and in 24 percent by CT.

FDG PET detected more metastatic sites (133 vs. 112), detecting significantly more bone and subcutaneous metastases, Bastiaannet and colleagues wrote. Treatment changed in 19 percent of patients; in 79 percent as a result of both scans, in 17 percent exclusively by FDG PET and in 4 percent exclusively by CT. In 14 percent of patients, FDG PET had an additional value over spiral CT, and in 9 percent of patients, CT had additional value over FDG PET.

As a result of FDG PET and CT, 27 percent of patients were upstaged, and treatment changed in one of five patients.

Based on their findings, the authors said that FDG PET and/or CT are indicated in the staging of patients with melanoma with palpable lymph node metastases.