CXCR4 and plasma cell myeloma: In contrast, splenic 68Ga-pentixafor uptake was not correlated with myeloma CXCR4 positivity of the scan (r = -0.154, P = 0.154), high-risk cytogenetics (r = -0.127, P = 0.306), the serum level of the involved free light chain (r = -0.115, P = 0.325), the pattern of myeloma bone marrow burden (focal vs. diffuse vs. focal-on-diffuse; r = -0.017, P = 0.873) or the number of PET-positive focal lesions (r = -0.153, P = 0.156).