CXCR4 and neoplasm: In the context of theragnostic approaches to MM, the major advantage of the PET tracer [68Ga]Ga-pentixafor is its potential for use in combination with the therapeutic lutetium-177 or yttrium-90 labeled pentixafor in progressive MM patients with CXCR4-positive tumor cells, as confirmed by a [68Ga]Ga-pentixafor PET scan.