CXCR4 and breast cancer: While a number of imaging agents targeting the CXCR4 receptors have been reported (e.g. [64Cu]AMD3100, [64Cu]AMD3465, 125I-12G5), the use of radiolabeled CXCR4-mAb as a companion diagnostic for MDX-1338 may be more beneficial in obtaining information on antibody biodistribution as made evident in 89Zr-trastuzumab and bevacizumab studies in patients with breast cancer [39].