CXCR4 expression determined by 68Ga-Pentixafor-PET/CT corresponded with advanced disease and was inversely associated with the number of previous treatment lines as compared to controls or untreated smouldering multiple myeloma patients (SUVpeakSpleen 4.06 ± 1.43 vs. 6.02 ± 1.16 vs. 7.33 ± 1.40; P < 0.001). The gene discussed is CXCR4; the disease is plasma cell myeloma.