(18)F-FDG PET-CT in detecting the primary tumor in patients with metastatic cancers of unknown primary origin / 中华肿瘤杂志

ABSTRACT

<p><b>OBJECTIVE</b>To evaluate the value of (18)F-FDG PET-CT in detecting the primary tumor in patients with metastatic cancers of unknown primary origin.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>(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.</p>