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The value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in carcinoma of an unknown primary: diagnosis and follow-up

Yapar, Zeynepa; Kibar, Mustafaa; Yapar, A. Fuatd; Paydas, Semrab; Reyhan, Mehmetd; Kara, Oguzb; Buyukdereli, Gulguna; Aydin, Mehmetd; Kelle, Aygul Polata; Unal, Ilkerc; Disel, Umute; Yavuz, Sinanb; Sahin, Berksoyb; Erkisi, Melekb

Nuclear Medicine Communications: January 2010 - Volume 31 - Issue 1 - p 59-66
doi: 10.1097/MNM.0b013e328332b340
Original Articles

Background The management of the patients with carcinoma of an unknown primary represents a difficult challenge in oncology. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) has provided new insights in the diagnosis, staging, and follow-up of oncological patients.

Aim This study aimed to investigate the value of FDG PET/CT in clarifying the primary site in our patients with histologically proven tumor metastasis (HPM) or with a high clinical suspicion of malignancy, and the clinical impact of this technique on the management of these patients.

Methods In total 94 patients from two centers underwent FDG PET/CT imaging; 78 patients with HPM and 16 patients with a clinical suspicion of malignancy. The histology and/or follow-up data were used as the gold standard. Hypermetabolic findings at the site of the pathological CT changes or at physiological FDG uptake sites were the criteria for malignancy. PET/CT findings were analyzed for the identification of the primary tumor site, for the relationship with survival, and also for the effect in chemotherapy monitoring.

Results Primary malignancy was discovered in 53 of 90 patients (59%) histologically and 37 (41%) patients' primary tumor sites were not found during the study period. Amongst 90 patients, five (6%) were normal on FDG PET/CT. Of 85 patients (94%) with pathological findings on FDG PET/CT, 27 patients (32%) had solitary and 58 (68%) patients had multiple organs affected. Regarding the whole study population, a sensitivity of 74% and a specificity of 78% were calculated for FDG PET/CT imaging. Regarding the patients with HPM, the sensitivity and specificity values were 84 and 81%, respectively. The mean survival time of the patients with disseminated disease was significantly shorter than those of the patients with single or no lesion (13.44±1.61, 20.98±2.0 and 26.67±2.73 months, respectively, P=0.014). In seven of eight patients, follow-up FDG PET/CT scans effectively monitored the patients' therapies.

Conclusion Whole-body FDG PET/CT has to be considered a useful method, especially in an early phase of the diagnostic workup of patients with carcinoma of an unknown primary syndrome, to optimize the management.

Departments of aNuclear Medicine

bMedical Oncology

cBiostatistics, Cukurova University Faculty of Medicine

Departments of dNuclear Medicine

eMedical Oncology, Başkent University Adana Hospital of Medical Faculty, Turkey

Correspondence to Dr Zeynep Yapar, MD, Department of Nuclear Medicine, Cukurova University School of Medicine, Balcali-Adana, Turkey

Tel: +90 322 338 7378; fax: +90 322 338 6486; e-mail:

Received 24 February 2009 Revised 4 June 2009 Accepted 2 August 2009

© 2010 Lippincott Williams & Wilkins, Inc.