Abstract
Purpose: To characterize the relationship between tumor uptake of 64Cu-DOTA-trastuzumab as measured by PET/CT and standard, immunohistochemistry (IHC)-based, histopathologic classification of human epidermal growth factor receptor 2 (HER2) status in women with metastatic breast cancer (MBC). Experimental Design: Women with biopsy-confirmed MBC and not given trastuzumab for [&ge] 2 months underwent complete staging, including 18F-fluorodeoxyglucose PET/CT. Patients were classified as HER2-positive (HER2+) or negative (HER2-) based on fluorescence in situ hybridization (FISH)-supplemented IHC of biopsied tumor tissue. Eighteen patients underwent 64Cu-DOTA-trastuzumab injection, preceded in 16 cases by trastuzumab infusion (45 mg). PET/CT was performed 21-25 (“Day 1”) and 47-49 (“Day 2”) h after 64Cu-DOTA-trastuzumab injection. Radiolabel uptake in prominent lesions was measured as maximum single-voxel standardized uptake value (SUVmax). Average intra-patient SUVmax (<SUVmax>pt) was compared between HER2+ and - patients. Results: Eleven women were HER2+ (8 IHC 3+, 3 IHC 2+/FISH amplified), while 7 were HER2- (3 IHC 2+/FISH non-amplified; 4 IHC 1+). Median <SUVmax>pt (Day 1, Day 2) was (6.6, 6.8 g/ml) for HER 2+ and (3.7, 4.3 g/ml) for HER2- patients (P<0.005 either day). The distributions of <SUVmax>pt overlapped between the two groups, and inter-patient variability was greater for HER2+ than HER2- disease (P<0.005 and 0.001, respectively, on Days1 and 2). Conclusion: By 1 day after injection, uptake of 64Cu-DOTA-trastuzumab in MBC is strongly associated with patient HER2 status. The variability within and among patients, as well as the overlap between the HER2+ and HER2- groups, suggests a role for 64Cu-DOTA-trastuzumab PET/CT in optimizing treatments that include trastuzumab.
- Copyright © 2017 by the Society of Nuclear Medicine and Molecular Imaging, Inc.