Clinical value of 18F-FDG PET-CT in detecting primary tumor for patients with carcinoma of unknown primary

Clinical value of 18F-FDG PET-CT in detecting primary tumor for patients with carcinoma of unknown primary: Publication year: 2012


Objective: 
To investigate the clinical value in detecting occult primary tumors with ¹⁸F-FDG PET-CT whole body imaging.

Methods: 
120 patients with unknown primary origin were referred for ¹⁸F-FDG PET-CT whole body imaging. All patients were performed ¹⁸F-FDG PET-CT whole body scan. PET-CT images were interpreted by visual inspection and semi-quantitative analysis (standardized uptake value, SUV). Histopathological and formal clinical follow-up findings were used to assess the value of FDG PET-CT.

Results: 
FDG PET-CT was able to detect the primary tumor in 54/120 patients (42.5%). The primary tumors were confirmed by histopathologic and formal clinical follow-up findings, and located in the head and neck (n =17), the lung (n =19), the breast (n =2), the esophagus (n =1), the stomach (n =2), the bile ducts (n =1), the pancreas (n =3), the co1on (n =3), the ovary (n =2), the prostate (n =l), others (n =3). FDG PET results were proved false positive in 9 patients (7.5%), which were located in the head and neck (n =3), the lung (n =1), the gastric (n =1), the colon (n =2), the ovary (n =1), the prostate (n =l).

During the clinical follow-up of median 32months (range, 2–45months), primary tumor was found in only 5 patients of 60 cases unidentified by PET-CT (breast cancer, gastric cancer, co1on cancer, prostate cancer and urinary tumors, respectively). The sensitivity, specificity, and accuracy of ¹⁸F-FDG PET-CT in the detection of the primary tumor site were 91.5%, 85.2%, and 88.3%, respectively.

Conclusion:
¹⁸F-FDG PET-CT whole body imaging is both a noninvasive and a very sensitive tomographic whole-body imaging modality, allowing for the detection of a primary tumor and complete tumor staging in single examination, which can contribute substantially to selecting appropriate therapeutic methods and evaluating prognosis. Perhaps ¹⁸F-FDG PET-CT whole body imaging should be used as a first-line imaging modality for patients with carcinoma of unknown primary rather than using it after other diagnostic procedures have failed to identify a primary tumor.