[(18)F-FDG PET-CT in detecting the primary tumor in patients with metastatic cancers of unknown primary origin].
OBJECTIVE
To evaluate the value of (18)F-FDG PET-CT in detecting the primary tumor in patients with metastatic cancers of unknown primary origin.


METHODS
Sixty-seven patients with metastatic cancers of unknown primary origin after extensive conventional diagnostic work-up were enrolled into this study. (18)F-FDG PET-CT scans were performed at approximately 60 minutes after the intravenous injection of 7.4 MBq (18)F-FDG/kg, then delayed imaging scans was done at approximately 180 minutes for detecting the primary focus. The standardized uptake value (SUV) >or= 2.5 on standard PET/CT imaging was considered as positive. Ten percent increase of retention index (RI) was also regarded as positive. The correlation between (18)F-FDG PET-CT results and histopathological and clinical findings were analyzed, and the SUV of detected primary focus and that of metastatic cancers were compared.


RESULTS
Of the 67 patients, the primary tumors were identified in 39 (53.7%) by (18)F-FDG PET-CT, and 36 of them were confirmed by pathology or follow-up. Thirteen distant metastases and seventeen lymphatic metastases were newly discovered by whole body (18)F-FDG PET-CT imaging. The SUV of metastatic tumors was significantly lower than that of primary tumors (t = 3.470,P = 0.001) and closely correlated with that of the primary tumors (r = 0.738, P = 0.000).


CONCLUSIONS
(18)F-FDG PET-CT is not only valuable in identifying the unknown primary tumor in patients with metastatic carcinoma, but can also be used to reveal the biological characteristics of the tumors by functional imaging.
Hu
Man
M
Department of Radiation Oncology, Shandong Cancer Hospital, Jinan 250117, China.
Li
Ming-Huan
MH
Kong
Li
L
Liu
Ning-Bo
NB
Yang
Guo-Ren
GR
Yu
Jin-Ming
JM
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000556:secondary; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000556:secondary; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging*; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods*; D014057:Tomography, X-Ray Computed
D019788:Fluorodeoxyglucose F18