Utility of FDG PET/CT and brain MRI in melanoma patients with increased serum S-100B level during follow-up.

Background: The serum level of the S-100B protein is increasingly used as a tumor marker in melanoma patients. The aims of this study were to assess the clinical relevance of increased S-100B during follow up of high-risk melanoma patients and to determine the value of subsequent whole-body PET/CT and brain MRI.

Methods: A retrospective analysis was performed of all 46 melanoma patients with a normal history and physical examination who were found to have an elevated serum S-100B level (> or =0.10 microg/L) during follow-up between August 2006 and March 2009. Suspicious lesions on FDG PET/CT were biopsied for histological or cytological confirmation or were imaged further and followed if no pathology confirmation could be obtained.

Results: The positive predictive value of an elevated serum S-100B was 50%. PET/CT revealed hypermetabolic lesions in 27 of the 46 patients (59%). PET/CT was never false negative as confirmed by median follow-up of 1 year but was false positive in 4 patients. MRI revealed brain metastases in 1 patient (2%). Of the 23 patients with a true positive PET/CT scan, 6 (26%) received surgical treatment with curative intent; the other 17 (74%) received palliative treatment or supportive care. The survival of patients with a normal PET/CT was longer than patients with a positive PET/CT (P = .002).

Conclusions: An elevated serum S-100B during follow-up of high-risk melanoma patients has a modest 50% positive predictive value for recurrent disease. Subsequent PET/CT and MRI can identify patients with recurrent disease.