CXCR4 and plasma cell myeloma: 68Ga-pentixafor, a radiolabeled peptide with high affinity for chemokine receptor 4 (CXCR4), which is involved in myeloma cell homing, bone marrow retention, angiogenesis and metastasis, has shown very promising results regarding both its diagnostic performance [42,43] and its potential application as a theranostic agent, identifying candidates suitable for CXCR4-directed therapies with β-emitting radionuclides such as lutetium-177 (177Lu).