UNLABELLED: Vascular endothelial growth factor (VEGF)-A is overexpressed in most malignant and premalignant breast lesions. VEGF-A can be visualized noninvasively with PET imaging and using the tracer (89)Zr-labeled bevacizumab. In this clinical feasibility study, we assessed whether VEGF-A in primary breast cancer can be visualized by (89)Zr-bevacizumab PET. METHODS: Before surgery, breast cancer patients underwent a PET/CT scan of the breasts and axillary regions 4 d after intravenous administration of 37 MBq of (89)Zr-bevacizumab per 5 mg. PET images were compared with standard imaging modalities. (89)Zr-bevacizumab uptake was quantified as the maximum standardized uptake value (SUV max). VEGF-A levels in tumor and normal breast tissues were assessed with enzyme-linked immunosorbent assay. Data are presented as mean ± SD. RESULTS: Twenty-five of 26 breast tumors (mean size ± SD, 25.1 ± 19.8 mm; range, 4-80 mm) in 23 patients were visualized. SUV max was higher in tumors (1.85 ± 1.22; range, 0.52-5.64) than in normal breasts (0.59 ± 0.37; range, 0.27-1.69; P