Patterns of _v3 Expression in Primary and Metastatic Human Breast Cancer as Shown by ¹⁸F-Galacto-RGD PET

¹ Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
² Department of Gynecology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
³ Department of Pathology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany

^* To whom correspondence should be addressed. E-mail: beer{at}roe.med.tum.de.

	Abstract

The integrin _v3 is a key player in angiogenesis and metastasis. Our aim was to study the uptake patterns of the _v3-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 _v3 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, 3.3 ± 0.8). SUVs in distant metastases were heterogeneous (2.9 ± 1.4). Immunohistochemistry confirmed _v3 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 _v3 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 _v3-targeted therapies are promising.

Key Words: breast cancer, integrins, _v3, angiogenesis, PET, RGD