Local recurrence of rectal cancer: evaluation with F-18 fluorodeoxyglucose PET imaging

Positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) is a useful technique for detection of malignancy. The purpose of this study was to determine if FDG-PET scanning using visual and quantitative analyses can identify patients with recurrent colorectal tumor following abdominoperineal resection.

Eighteen patients were evaluated for possible local recurrence of rectal carcinoma following abdominoperineal resection. The clinical presentation included rising carcinoembryonic antigen levels (n = 5), increasing size of a presacral mass on computed tomography or magnetic resonance (n = 13), or local symptoms (n = 3). Axial PET images of the pelvis were obtained following an injection of 10 mCi of FDG prior to biopsy. Quantitative analysis was performed by calculation of a standardized uptake ratio (SUR), and the images were interpreted by two radiologists in consensus. FDG-PET findings were correlated with histological or cytological findings and with the clinical outcome.

Recurrent malignancy was confirmed in 13 patients by surgery (n = 8) or percutaneous biopsy (n = 5). Benign lesions were confirmed in five patients by surgery (n = 1), biopsy (n = 3), or clinical follow up (n = 1). Visual analysis of the FDG-PET data had a sensitivity of 92.3% (12/13) for recurrent disease (95% confidence limits; 63.9%, 99.8%) and a specificity of 80% (4/5; 95% confidence limits; 28.3%, 99.4%). SUR values were significantly higher in malignant lesions (range = 2.92-19.74, mean = 6.89) than in benign ones (range = 1.40-3.47, mean = 1.96; p = 0.002).

FDG-PET is an accurate technique for detection of locally recurrent colorectal carcinoma. Visual analysis is equivalent to quantitative analysis for detection of disease.