Role of 18 F-FDG PET/CT vs CT-scan in patients with pulmonary metastases previously operated on for colorectal liver metastases.

OBJECTIVE: There is currently no conclusive scientific evidence available regarding the role of the 18 F-FDG PET/CT for detecting pulmonary metastases from colorectal cancer (PMCRC) in patients operated on for colorectal liver metastases (CRLM). In the follow up of patients who underwent surgery for CRLM, we compare CT-scan and 18 F-FDG PET/CT in patients with PMCRC.

METHODS: We designed the study prospectively performing an 18 F-FDG PET/CT on all patients operated on for CRLM where the CT-scan detected PMCRC during the follow up. We included patients who were operated on for PMCRC because the histological findings were taken as a control rather than biopsies.

RESULTS: Of the 101 pulmonary nodules removed from 57 patients, the CT-scan identified a greater number (89 nodules) than the 18 F-FDG PET/CT (75 nodules) (p < 0.001). Sensitivity was greater with the CT-scan (90 vs 76%, respectively) with a lower specificity (50 vs 75%, respectively) than with the 18 F-FDG PET/CT. There were no differences between positive-predictive value and negative-predictive value. The 18 F-FDG PET/CT detected more pulmonary nodules in four patients (one PMCRC in each of these patients) and more extrapulmonary disease in six patients (four mediastinal lymph nodes, one retroperitoneal lymph node and one liver metastases) that the CT-scan had not detected.

CONCLUSION: Although CT-scans have a greater capacity to detect PMCRC, the 18 F-FDG PET/CT could be useful in the detection of more pulmonary and extrapulmonary disease not identified by the CT-scan. Advances in knowledge: We tried to clarify the utility of 18 F-FDG PET/CT in the management of this subpopulation of patients.