18F-Fluorodeoxyglucose-positron Emission Tomography/Computed Tomography Imaging of Metastatic Nasopharyngeal Cancer with Emphasis on the Distribution of Bone Metastases.

Distant metastases change the prognosis of patients with nasopharyngeal carcinoma (NPC) which most commonly metastasizes to the bone. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is reported as useful in imaging NPC metastases. Our study assesses the incidence and distribution of bone metastases detected by 18F-FDG PET/CT in NPC. 717 18F-FDG PET/CT scan reports of histologically proven NPC patients imaged in Singapore General Hospital, Singapore, between 2003 and 2009 were reviewed for the total number of metastases (scanned from vertex to mid-thigh) and analyzed for distribution. Of the 709 FDG avid metastases in these reports, 357/709 (50.35%) were locoregional nodal metastasis and 352/709 (49.65%) were distant metastases of which 192/709 (27.08%) of total metastases and 54.54% of distant metastases (192/352) were in the bones. The majority of the bone lesions 125/192 (65.1%) were in the axial skeleton with 109/192 (56.77%) in the lower skeleton (thoracolumbar spine, sacrum, and pelvis). The incidence of bone metastases in our study (27.08%) was higher than that reported in other studies, for example, 15% by Liu et al. and 11% (230 patients) by Caglar et al. Bone metastases have been reported in the femurs and the feet and as such some metastases may have been outside the field of view of the scans. In our study, 27% of FDG avid NPC metastases are in the bones.

The incidence and sites of Nasopharyngeal carcinoma (NPC) metastases on FDG PET/CT scans.

INTRODUCTION: The only investigation to determine if a whole body FDG PET/CT scan is helpful in the evaluation of NPC is a study from Stanford. In this study, 26 patients with whole body PET/CT, were evaluated for lesions below adrenals and showed that 7.7% of distant metastases were below adrenals. Our study comparing distant metastases below diaphragm with Stanford study to evaluate the need for whole body PET/CT. MATERIAL AND METHODS: Reports of NPC patients in Singapore General Hospital were reviewed. The lesions were analyzed for total number and number below diaphragm. The lesions below the diaphragm were further analyzed if they were solitary or involved multiple areas and if any additional lesions were above diaphragm. RESULTS: 717 reports were included in final analysis. The number of FDG avid lesions in these reports was 709. Distant metastases represented 352 of the 709 lesions. The number of lesions below diaphragm was 152, of the lesions below diaphragm only 16 of lesions have no co-existing distant metastases above diaphragm. From these lesions, there were only 12 solitary lesions. The other 4 has concurrent metastases but all localized below diaphragm. CONCLUSION: Compared to Stanford study, number of reports is more representative in this study and the yield is much lower (7.7% versus 2.26%). From the results of our study we can consider limiting the scan area from vertex to below diaphragm. However, the symptoms and clinical presentation of the patient will further direct the requesting physician in the area to be imaged.

Perinephric urinoma due to locally advanced recto-sigmoid tumor: incidental finding on bone scan.

We are presenting a 59 years old man with locally advanced recto-sigmoid colon cancer; complaining of left flank pain and bone scan was done to rule out bone metastases. Findings in bone scan were suggesting left renal obstruction, but further SPECT/CT imaging to localize the uptake revealed a perinephric collection likely due to leak from the left ureter close to tumor site.