The role of FDG-PET/CT in preoperative staging of sentinel lymph node biopsy-positive melanoma patients.

BACKGROUND: On April 1, 2015, Odense University Hospital (OUH) began a new diagnostic strategy, wherein all malignant melanoma (MM) patients in the Region of Southern Denmark with a positive sentinel lymph node biopsy (SLNB) underwent FDG-PET/CT preoperatively prior to lymph node dissection (LND). The purpose of this study is to determine FDG-PET/CT's efficacy in finding distant metastasis in the first year after the implementation of this new strategy, and to what extent these findings influence subsequent diagnostic testing and treatment in this patient group. We conducted a retrospective multicenter cohort study which included all patients with MM from all hospitals in the Region of Southern Denmark from April 1, 2015 to April 1, 2016 found to be SLNB-positive who subsequently underwent FDG-PET/CT. Patient information was acquired from the Danish Melanoma Database and was cross-referenced with OUH's patient records. The data was analyzed for a number of parameters including FDG-PET/CT findings and treatment strategy. Median follow-up time was 7 months.

RESULTS: A total of 47 patients were eligible from the first year of this new diagnostic strategy. One patient was excluded due to undergoing LND prior to FDG-PET/CT. Thus, 46 patients were included in this study. Ultimately, preoperative FDG-PET/CT neither uncovered any distant metastases nor led to any alterations in treatment strategy in this patient group.

CONCLUSIONS: Surprisingly, this new diagnostic strategy did not find any MM metastases or uncover anything else of relevance. FDG-PET/CT did, however, provide false positive findings in 13 % (6/46) of these patients. These scans triggered additional, predominantly invasive, procedures, which did not ultimately have an impact on the therapeutic strategy. Thus, these findings indicate a need for re-evaluation of this new diagnostic strategy as well as the necessity for further clinical trials evaluating FDG-PET/CT's utility in this clinical setting.