Patterns of avb3 Expression in Primary and Metastatic Human Breast Cancer as Shown by 18F-Galacto-RGD PET

The integrin avb3 is a key player in angiogenesis and metastasis. Our aim was to study the uptake patterns of the avb3-selective PET tracer 18F-galacto-RGD in invasive ductal breast cancer. Methods: Sixteen patients with primary (n 5 12) or metastasized breast cancer (n 5 4) were examined with 18F-galacto-RGD PET. Standardized uptake values (SUVs) were derived by region-ofinterest analysis, and immunohistochemistry of avb3 expression was performed (n5 5). Results: 18F-Galacto-RGD PET identified all invasive carcinomas, with SUVs from 1.4 to 8.7 (mean 6 SD, 3.6 6 1.8; tumor-to-blood and tumor-to-muscle ratios, 2.7 6 1.6 and 6.2 6 2.2, respectively). Lymph-node metastases were detected in 3 of 8 patients (mean SUV, 3.36 0.8). SUVs in distant metastases were heterogeneous (2.96 1.4). Immunohistochemistry confirmed avb3 expression predominantly on microvessels (5/5) and, to a lesser extent, on tumor cells (3/5). Conclusion: Our results suggest generally elevated and highly variable avb3 expression in human breast cancer lesions. Consequently, further imaging studies with 18F-galacto-RGD PET in breast cancer patients for assessment of angiogenesis or planning of avb3-targeted therapies are promising.