LOCAL RECURRENCE OF RECTAL-CANCER - EVALUATION WITH F-18 FLUORODEOXYGLUCOSE PET IMAGING

Background: Positron emission tomography (PET) with F-18 fluorodeoxygl ucose (FDG) is a useful technique for detection of malignancy. The pur pose of this study was to determine if FDG-PET scanning using visual a nd quantitative analyses can identify patients with recurrent colorect al tumor following abdominoperineal resection. Methods: Eighteen patie nts were evaluated for possible local recurrence of rectal carcinoma f ollowing abdominoperineal resection. The clinical presentation include d 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 obtain ed following an injection of 10 mCi of FDG prior to biopsy. Quantitati ve analysis was performed by calculation of a standardized uptake rati o (SUR), and the images were interperated by two radiologists in conse nsus. FDG-PET findings were correlated with histological or cytologica l findings and with the clinical outcome. Results: Recurrent malignanc y was confirmed in 13 patients by surgery (n = 8) or percutaneous biop sy (n = 5). Benign lesions were confirmed in five patients by surgery (n = 1), biopsy (n = 3), or clinical follow up (n = 1). Visual analysi s 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 signific antly higher in malignant lesions (range = 2.92-19.74, mean = 6.89) th an in benign ones (range = 1.40-3.47, mean = 1.96; p = 0.002). Conclus ion: FDG-PET is an accurate technique for detection of locally recurre nt colorectal carcinoma. Visual analysis is equivalent to quantitative analysis for detection of disease.