CXCR4 and neoplasm: Weiss et al. investigated 64Cu-AMD3100, a radiolabelled CXCR4 antagonist, and demonstrated high tumor selectivity and strong tumor-to-muscle and tumor-to-blood ratios, making it a viable option for non-invasive quantification of CXCR4 expression to inform treatment decisions (Weiss et al., 2012).