Role of ¹⁸F-FDG dual-head gamma-camera coincidence imaging in recurrent or metastatic colorectal carcinoma

¹⁸F-FDG PET has been shown to be of high diagnostic accuracy for the evaluation of recurrent colorectal cancer. However, the limited availability of PET scanners precludes ¹⁸F-FDG assessment of many patients for whom the study is indicated. An alternative is the SPECT system in coincidence mode. The aim of this study was to determine the role of dual-head camera ¹⁸F-FDG coincidence imaging (DHC ¹⁸F-FDG) in patients with recurrent colorectal cancer. Methods: Sixty-seven DHC ¹⁸F-FDG studies were performed on 62 patients with suspected recurrent colorectal cancer. Reports of contemporary CT were available for the purpose of correlation for 61 of the studies. The final diagnosis of the imaging findings was based on histology or clinical and imaging follow-up of at least 6 mo. Results: In lesion-based analysis, 103 tumor sites were suspected on DHC ¹⁸F-FDG, CT, or colonoscopy. Ninty-three of them were found to be true tumor sites. For DHC ¹⁸F-FDG, the sensitivity was 88%, specificity was 80%, positive predictive value (PPV) was 98%, negative predictive value (NPV) was 42%, and accuracy was 87%. For CT, the sensitivity was 63%, specificity was 10%, PPV was 85%, NPV was 3%, and accuracy was 57%. In patient-based analysis, DHC ¹⁸F-FDG differentiated patients with recurrent cancer from disease-free patients with a sensitivity of 91%, specificity of 73%, PPV of 94%, NPV of 62%, and accuracy of 88%. DHC ¹⁸F-FDG detected tumor sites in 12 (67%) of 18 patients with elevated carcinoembryonic antigen and negative CT findings. Conclusion: DHC ¹⁸F-FDG is an adequate readily available technique for assessment of recurrent colorectal cancer and has a diagnostic accuracy better than that of CT.