Objective: The purpose of this study is to evaluate the added value of FDG PET/CT for the management of additional lesions detected by breast MRI during initial staging of known breast cancer.
Materials and methods: We retrospectively queried our database for all consecutive patients with biopsy-confirmed breast cancer who underwent breast MRI and FDG PET/CT before neoadjuvant chemotherapy between November 2011 and November 2012. The final population comprised 80 patients. Initially, two readers retrospectively analyzed the breast MRI data for the presence of lesions in addition to the previously confirmed index neoplasm. Analysis of FDG PET/CT data followed; two different readers evaluated the presence or absence of FDG uptake in both breasts. The reference standard for additional lesions was percutaneous biopsy with subsequent 2-year follow-up for benign results. Statistical analysis was conducted with nonparametric analysis and the Fisher exact test.
Results: The readers detected 61 additional breast lesions at MRI in 45 patients (56.2%); 37 of 61 (61%) additional lesions were malignant and 24 of 61 (39%) were benign. Among the 61 additional breast lesions detected by MRI, only 32 were positive at FDG PET/CT, with a positive predictive value of 90.6% and negative predictive value of 72%. The sensitivity, specificity, and accuracy of FDG PET/CT were 78.3%, 87.5%, and 81.9%, respectively. In eight cases, FDG PET/CT missed additional malignant lesions. All missed malignant additional lesions were smaller than 1 cm. In three cases, additional lesions also detected at FDG PET/CT were benign.
Conclusion: In the case of additional lesions detected at MRI, a negative FDG PET/CT finding could replace a breast biopsy for lesions larger than 1 cm.
Keywords: FDG PET/CT; MRI; additional lesion; breast; cancer.