In situ validation of VEGFR-2 and α _v ß ₃ integrin as targets for breast lesion characterization

Vascular endothelial growth factor receptor 2 (VEGFR-2) and α _v ß ₃ integrin are the most frequently addressed targets in molecular imaging of tumor angiogenesis. In preclinical studies, molecular imaging of angiogenesis has shown potential to detect and differentiate benign and malignant lesions of the breast. Thus, in this retrospective clinical study employing patient tissues, the diagnostic value of VEGFR-2, α _v ß ₃ integrin and vascular area fraction for the diagnosis and differentiation of breast neoplasia was evaluated. To this end, tissue sections of breast cancer (n = 40), pre-invasive ductal carcinoma in situ (DCIS; n = 8), fibroadenoma (n = 40), radial scar (n = 6) and normal breast tissue (n = 40) were used to quantify (1) endothelial VEGFR-2, (2) endothelial α _v ß ₃ integrin and (3) total α _v ß ₃ integrin expression, as well as (4) the vascular area fraction. Sensitivity and specificity to differentiate benign from malignant lesions were calculated for each marker by receiver operating characteristics (ROC) analyses. Whereas vessel density, as commonly used, did not significantly differ between benign and malignant lesions (AUROC: 0.54), VEGFR-2 and α _v ß ₃ integrin levels were gradually up-regulated in carcinoma versus fibroadenoma versus healthy tissue. The highest diagnostic accuracy for differentiating carcinoma from fibroadenoma was found for total α _v ß ₃ integrin expression (AUROC: 0.76), followed by VEGFR-2 (AUROC: 0.71) and endothelial α _v ß ₃ integrin expression (AUROC: 0.68). In conclusion, total α _v ß ₃ integrin expression is the best discriminator between breast cancer, fibroadenoma and normal breast tissue. With respect to vascular targeting and molecular imaging of angiogenesis, endothelial VEGFR-2 appeared to be slightly superior to endothelial α _v ß ₃ for differentiating benign from cancerous lesions.