Cancer of unknown primary origin: Can FDG PET/CT have a role in detecting the site of primary?

Objectives: Our aim in this study was to evaluate the efficiency of combined positron emission tomography and computed tomography (PET/CT), in the detection of the primary tumor origin in patients with cancer of unknown primary (CUP). Methods: PET/CT were performed for 52 patients with CUP. These patients presented with metastatic lesions that were proven pathologically, and no primary site was detected by previous investigations. Results: The number of patients with true positive primary tumor sites was 29 (55.8%), 4 patients with false positive results (7.7%), 9 patients with true negative results (17.3%) and 10 patients with false negative results (19.2%). The sensitivity was 74.4%, specificity was 69.2% and accuracy was 73.1%. Our positive predictive value in this study was 87.9% and our negative predictive value for this study was 47.4%. Conclusions: This study showed an advantage of PET/CT in the detection of the site of the primary tumor in patients diagnosed with CUP. Keywords: Carcinoma of unknown primary, Detection of unknown primary tumor, 2-(18F)-fluoro-2-deoxy-d-glucose, Combined computed tomography and positron emission tomography