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Prognostic Relevance of 18F-FDG PET/CT in Carcinoma of Unknown Primary

Breuer, Niklas MD*; Behrendt, Florian F. MD*; Heinzel, Alexander MD*; Mottaghy, Felix M. MD*†; Palmowski, Moritz MD*; Verburg, Frederik A. MD, PhD*†

doi: 10.1097/RLU.0000000000000304
Original Articles

Objectives The aim of this study was to assess whether 18F-FDG PET combined with x-ray CT (18F-FDG PET/CT) findings have a prognostic impact in patients with carcinoma of unknown primary (CUP).

Patients and Methods Seventy patients with CUP who were referred for 18F-FDG PET/CT were included. 18F-FDG PET/CT results were checked against available histologic diagnosis and follow-up data. For each patient, the SUVmax of the lesion with maximum uptake was measured.

Results In 26% of the patients, a primary tumor was identified. The follow-up period after 18F-FDG PET/CT scan ranged between 3 and 45 months. Kaplan-Meier analysis revealed 1-year survival rates of 92% in the group without evidence of malignancy on 18F-FDG PET/CT, 78% in the group with locoregional disease, and 34% in the group with extensive disease on 18F-FDG PET/CT. Three-year survival rates in these groups were 73%, 71%, and 23%, respectively (P = 0.001). There was no significant survival difference between patients with regionally confined disease without identification of the primary tumor and those in whom the primary tumor was identified on 18F-FDG PET/CT (P = 0.25). This was also the case for patients with extensive disease (P = 0.26). The SUVmax of the lesion with maximum uptake was not significantly related to survival (P = 0.56).

Conclusions 18F-FDG PET/CT is a helpful tool for the identification of the primary tumor in patients with CUP; it is also able to provide an accurate assessment of prognosis based on the extent of the disease without the need for identification of the primary tumor.

From the *Department of Nuclear Medicine, University Hospital Aachen, Aachen, Germany; and †Department of Nuclear Medicine, Maastricht University Medical Center, Maastricht, the Netherlands.

Received for publication May 2, 2013; revision accepted October 17, 2013.

Conflicts of interest and sources of funding: none declared.

Reprints: Frederik A. Verburg, MD, PhD, Department of Nuclear Medicine, University Hospital Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany. E-mail:

© 2014 by Lippincott Williams & Wilkins