Usefulness of FDG-PET scan in the assessment of suspected metastatic or recurrent adenocarcinoma of the colon and rectum

PURPOSE: The purpose of this study was to evaluate the clinical efficacy of positron emission tomography with 2-[¹⁸F] fluoro-2-deoxy-D-glucose compared with computed tomography plus other conventional diagnostic studies in patients suspected of having metastatic or recurrent colorectal adenocarcinoma. METHODS: The records of 105 patients who underwent 101 computed tomography and 109 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography scans for suspected metastatic or recurrent colorectal adenocarcinoma were reviewed. Clinical correlation was confirmed at time of operation, histopathologically, or by clinical course. RESULTS: The overall sensitivity and specificity of 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography in detection of clinically relevant tumor were higher (87 and 68 percent) than for computed tomography plus other conventional diagnostic studies (66 and 59 percent). The sensitivity of 2-[¹⁸F] fluoro- 2-deoxy-D-glucose positron emission tomography in detecting mucinous cancer was lower (58 percent; n = 16) than for nonmucinous cancer (92 percent; n = 93). The sensitivity of 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting locoregional recurrence (n = 70) was higher than for computed tomography plus colonoscopy (90 vs. 71 percent, respectively). The sensitivity of 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting hepatic metastasis (n = 101) was higher than for computed tomography (89 vs. 71 percent). The sensitivity of 2-[¹⁸F] fluoro- 2-deoxy-D-glucose positron emission tomography in detecting extrahepatic metastases exclusive of locoregional recurrence (n = 101) was higher than for computed tomography plus other conventional diagnostic studies (94 vs. 67 percent). 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography altered clinical management in a beneficial manner in 26 percent of cases (26/101) when compared with evaluation by computed tomography plus other conventional diagnostic studies. CONCLUSION: 2-[¹⁸F] fluoro-2-deoxy-D- glucose positron emission tomography is more sensitive than computed tomography for the detection of metastatic or recurrent colorectal cancer and may improve clinical management in one-quarter of cases. However, 2-[¹⁸F] fluoro-2-deoxy-D-glucose positron emission tomography is not as sensitive in detecting mucinous adenocarcinoma, possibly because of the relative hypocellularity of these tumors.