Detection of primary tumor by 18F-FDG PET/CT in cancer of unknown primary (+ Running poster)

Abstract

Patients with carcinoma of unknown primary are a diverse and heterogenous group. There are various clinical manifestations and some of the patients could be asymptomatic and diagnosed incidentally. Among numerous imagining techniques, PET/CT seems to be the most suitable for localizing the primary tumor. The sensitivity of PET/CT in detecting primary tumor is 29%–69% according different authors and it is higher comparing to contrast enhanced CT. The purpose of this retrospective study was to estimate the detection ratio of 18F-FDG PET-CT in highlighting the sites of primary tumors in patients with carcinoma of unknown primary. Sixty-seven patients with cancer of unknown primary (39 males, 28 females, the mean age was about 62 years), unsuccessfully investigated with conventional diagnostic procedures and laboratory investigation, were enrolled for 18F-FDG PET-CT whole body imaging. Patients received 370 MBq FDG (10 mCi) intravenously, and whole body images were acquired at 60 min after injection. The images obtained were analyzed with visual and semi-quantitative methods. The primary tumor site was correctly identified by 18F-FDG PET/CT in 23 patients (23/67; 34.3%): gastrointestinal tract ( n = 6), lung ( n = 4), rino/oro-pharynx ( n = 4), mammary gland ( n = 2), lymphatic system ( n = 2), prostate gland ( n = 1), thyroid ( n = 1), parotid gland ( n = 1), bladder ( n = 1), and kidney ( n = 1). Our study suggests that 18F-FDG PET-CT is a useful noninvasive imaging tool to locate the primary tumor in patients with unknown primary malignancies, with high impact in clinical management and plan therapeutic strategies.