Abstract
Invasive lobular carcinoma (ILC) demonstrates lower conspicuity on 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET than the more common invasive ductal carcinoma (IDC). Other molecular imaging methods may be needed for evaluation of this malignancy. As ILC is nearly always (95%) estrogen receptor (ER) positive, ER-targeting PET tracers such as 16α-[18F]-fluoroestradiol ([18F]FES) may have value. We reviewed prospective trials at Memorial Sloan Kettering Cancer Center (MSK) utilizing [18F]FES PET/CT to evaluate metastatic ILC patients with synchronous [18F]FDG and [18F]FES PET/CT imaging, which allowed a head-to-head comparison of these two PET tracers. Methods: Six prospective clinical trials utilizing [18F]FES PET/CT in patients with metastatic breast cancer were performed at MSK from 2008-2019. These trials included 92 patients, of which 14 (15%) were of ILC histology. Seven of 14 patients with ILC had an [18F]FDG PET/CT performed within 5 weeks of the research [18F]FES PET/CT and no intervening change in management. For these 7 patients, the [18F]FES and [18F]FDG PET/CT studies were analyzed to determine the total number of tracer avid lesions, organ systems of involvement, and SUVmax of each organ system for both tracers. Results: In the seven comparable pairs of scans, there were a total of 254 [18F]FES-avid lesions (SUVmax 2.6 to 17.9) and 111 [18F]FDG-avid lesions (SUVmax 3.3 to 9.9) suspicious for malignancy. For 5 of 7 (71%) of ILC patients, [18F]FES PET/CT detected more metastatic lesions than [18F]FDG PET/CT. In the same 5 of 7 patients, the SUVmax of [18F]FES-avid lesions was greater than the SUVmax of [18F]FDG-avid lesions. One patient had [18F]FES avid metastases with no corresponding [18F]FDG avid metastases. There were no patients with [18F]FDG avid distant metastases without [18F]FES avid distant metastases, although in one patient liver metastases were evident on [18F]FDG but not [18F]FES PET. Conclusion: [18F]FES PET/CT compared favorably with [18F]FDG PET/CT for detection of metastases in patients with metastatic ILC. Larger prospective trials of [18F]FES PET/CT in ILC should be considered to evaluate ER-targeted imaging for clinical value in patients with this histology of breast cancer.
- Copyright © 2020 by the Society of Nuclear Medicine and Molecular Imaging, Inc.