(18)Fluorodeoxyglucose positron emission tomography to detect mediastinal or internal mammary metastases in breast cancer

Purpose: To determine the prevalence of suspected disease in the mediastinu m and internal mammary (IM) node chain by (18)fluorodeoxyglucose (FDG) posi tron emission tomography (PET), compared with conventional staging by compu ted tomography (CT) in patients with recurrent or metastatic breast cancer. Patients and Methods: We retrospectively evaluated intrathoracic lymph node s using FDG PET and CT data in 73 consecutive patients with recurrent or me tastatic breast cancer who had both CT and FDG PET within 30 days of each o ther. In reviews of CT scans, mediastinal nodes measuring I cm or greater i n the short axis were considered positive. PET was considered positive when there were one or more mediastinal foci of FDG uptake greater than the med iastinal blood pool. Results: Overall, 40% of patients had abnormal mediastinal or IM FDG uptake consistent with metastases, compared with 23% of patients who had suspicio usly enlarged mediastinal or IM nodes by CT. Both FDG PET and CT were posit ive in 22%. In the subset of 33 patients with assessable follow-up by CT or biopsy, the sensitivity, specificity, and accuracy for nodal disease was 8 5%, 90%, and 88%, respectively, by FDG PET, 54%, 85%, and 73%, respectively , by prospective interpretation of CT, and 50%, 83%, and 70%, respectively, by blinded observer interpretation of CT. Among patients suspected of havi ng only locoregional disease recurrence (n = 33), 10 had unsuspected medias tinal or IM disease by FDG PET. Conclusion: FDG PET may uncover disease in these nodal regions not recogniz ed by conventional staging methods. Future prospective studies using histop athology for confirmation are needed to validate the preliminary findings o f this retrospective study.