Rahi Kumar BS, Presenter: Nothing to Disclose

Randall A. Hawkins MD, PhD, Abstract Co-Author: Nothing to Disclose

Benjamin M. Yeh MD, Abstract Co-Author: Pending research grant, General Electric Company Research grant, Bayer AG

Zhen Jane Wang MD, Abstract Co-Author: Nothing to Disclose

To retrospectively evaluate the rate of malignancy of focal 18F-FDG-avid lesions without CT correlate at whole body PET-CT in oncology patients, since knowledge of any patterns and the risk of malignancy of these lesions may facilitate patient management.

We performed a computer search of all PET-CT studies performed at our institution from 2006 to 2009, and identified 87 studies with findings of focal 18F-FDG-avid lesions without correlate at CT. The rate of malignancy of such lesions was determined by reviewing findings at follow-up imaging, or by clinical, or histopathologic follow-up. Rates of malignancy were compared by lesion location and by the type of primary malignancy.

The common locations for focal 18F-FDG-avid lesions without CT correlate were: lymph node location (without visible lymph nodes) (27/87), bone (21/87), liver (9/87), muscle (8/87), and gastrointestinal tract (7/87). 41% (36/87) of the focal FDG-avid lesions without CT correlate were malignant (either metastatic disease or a second malignancy) at follow up (mean follow-up: 5 months, range: 1-25 months). Focal FDG-avid lesions in lymph node location and in bone without CT correlate had higher rates of malignancy (56%, 15/27, and 52%, 11/21, respectively) than lesions in all other locations (26%, 10/39, P=.028). In 15 of 87 cases, the only remarkable finding at PET-CT was an FDG-avid lesion without CT correlate. Of those, 53% (8/15) were positive for malignancy. There were no significant differences in the rates of malignancy for the focal FDG-avid lesions without CT correlate when stratified by the type of primary malignancy in this series.

Focal FDG avid lesions without CT correlate were malignant in 41% cases in our series of oncology patients. Lesions in lymph node location and in bones had the highest rates of malignancy.

Knowledge of the patterns and risk of malignancy of focal FDG-avid lesions without CT correlate in oncology patients may facilitate management of oncology patients with such lesions on PET-CT.

Kumar, R, Hawkins, R, Yeh, B, Wang, Z, Focal 18F-FDG-avid Lesions without CT Correlate at Whole Body PET-CT in Oncology Patients: How Often Are They Malignant?.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9008816.html