Role of 18F-FDG PET/CT in identifying distant metastatic disease missed by conventional imaging in patients with locally advanced breast cancer.

This study was conducted to evaluate the role of 18F-fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in identifying missed distant metastases in patients with locally advanced breast cancer (LABC) who were assessed by conventional imaging methods. Forty-three consecutive patients with histopathologically proven LABC with negative conventional imaging results for distant metastases were included in the study. All of them underwent 18F-FDG PET/CT within a week after conventional imaging. 18F-FDG PET/CT findings suggestive of distant metastases were noted in 11/43 patients, and 10 of them were confirmed to have true-positive distant metastatic disease on clinical follow-up of 6 months. None of the patients with negative 18F-FDG PET/CT for distant metastases developed distant metastases during the follow-up. 18F-FDG PET/CT had a sensitivity, specificity, positive predictive value, and negative predictive value of 100, 96.8, 91, and 100%, respectively, for identifying distant metastases missed by conventional imaging. In addition, 18F-FDG PET/CT suggested previously unknown lymph nodal metastases in 16/43 (37%) patients. Change in stage was noticed in 17/43 (39.5%) patients. 18F-FDG PET/CT is a sensitive and specific imaging modality for identifying distant metastases in patients with LABC missed by conventional imaging. In addition, it detects unknown lymph nodal metastases in a significant proportion of patients and hence can be used routinely in staging of patients with LABC.