Metastases from Unknown Primary Tumor. PET-FDG as Initial Diagnostic Procedure?

Purpose: To analyze the efficacy and impact on management of PET-FDG in patients with metastases from unknown primary tumor.Procedures: Retrospective analysis of 24 patients referred to the PET center for metastasis of unknown primary after a negative imaging workup. PET results were validated by means of oriented imaging, follow-up or biopsy when ethically justified.Results: PET identified the primary tumor in 13/24 (54%) of patients: breast (n = 1), lung (n = 9), colon (n = 1), stomach (n = 1) and mouth (n = 1). The false positive rate of PET was 21% (5/24). PET was shown to affect the management of 10/24 patients (42%).Conclusion: Whole body PET-FDG was more effective than conventional imaging methods in detecting unknown primary tumors. PET altered patient management in 42% of cases. PET should be performed prior to other investigations in such patients and could avoid unnecessary and often unfruitful diagnostic procedures.