Patterns of α_vβ₃ expression in primary and metastatic human breast cancer as shown by ¹⁸F-galacto-RGD PET

The integrin α_vβ₃ is a key player in angiogenesis and metastasis. Our aim was to study the uptake patterns of the α_vβ₃-selective PET tracer ¹⁸F- galacto-RGD in invasive ductal breast cancer. Methods: Sixteen patients with primary (n = 12) or metastasized breast cancer (n = 4) were examined with ¹⁸F-galacto-RGD PET. Standardized uptake values (SUVs) were derived by region-of-interest analysis, and immunohistochemistry of α _vβ₃ expression was performed (n = 5). Results: ¹⁸F-Galacto-RGD PET identified all invasive carcinomas, with SUVs from 1.4 to 8.7 (mean ± SD, 3.6 ± 1.8; tumor-to-blood and tumor-to-muscle ratios, 2.7 ± 1.6 and 6.2 ± 2.2, respectively). Lymph-node metastases were detected in 3 of 8 patients (mean SUV, 3.360.8). SUVs in distant metastases were heterogeneous (2.9 ± 1.4). Immunohistochemistry confirmed α_vβ₃ 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 α_vβ₃ 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 α_vβ₃-targeted therapies are promising.