Comparison of F-18 FDG PET and CT in differentiation of pulmonary metastasis from benign lung lesion in patients with colon cancer

Abstract

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Objectives: Although lung is common metastatic site from colon cancer, chest CT is not a routine follow-up test to detect recurrence. The purpose of this study was to compare the diagnostic performance of FDG PET with that of chest CT in detecting pulmonary metastasis from colon cancer.

Methods: From 1999 to 2005, 476 FDG PET studies were performed to detect recurrence in patients with colon cancer. A total of 92 studies which were performed to assess lung metastasis were enrolled (M:F=59:33, age: 58.5±11.1). Chest CT results obtained within 2 months from PET were compared. Diagnosis of pulmonary metastasis was confirmed by biopsy or serial chest CT follow-up over 1 year.

Results: Pulmonary metastasis was confirmed in 69 patients. Twenty-three patients were confirmed to have benign lesion. FDG PET showed sensitivity of 78% and specificity of 65%, while chest CT showed sensitivity of 96% and specificity of 43%. Of 15 false negative FDG PET, 13 had small multiple nodules less than 10 mm in size, and 2 had single mucinous metastasis. Of 13 false positive CT, all lesions were confirmed to be benign granuloma.

Conclusions: Although chest CT was more sensitive than FDG PET in detecting small pulmonary metastasis from colon cancer, FDG PET was more specific. FDG PET would be useful to evaluate solitary lung metastasis and to exclude benign granuloma.