Improved Primary Staging of Marginal-Zone Lymphoma by Addition of CXCR4-Directed PET/CT.

Abstract

PET/CT with ¹⁸F-FDG is an integral component in the primary staging of most lymphomas. However, its utility is limited in marginal-zone lymphoma (MZL) because of inconsistent ¹⁸F-FDG avidity. One diagnostic alternative could be the targeting of C-X-C motif chemokine receptor 4 (CXCR4), shown to be expressed by MZL cells. This study investigated the value of adding CXCR4-directed ⁶⁸Ga-pentixafor PET/CT to conventional staging. <b>Methods:</b> Twenty-two newly diagnosed MZL patients were staged conventionally and with CXCR4 PET/CT. Lesions identified exclusively by CXCR4 PET/CT were biopsied as the standard of reference and compared with imaging results. The impact of CXCR4-directed imaging on staging results and treatment protocol was assessed. <b>Results:</b> CXCR4 PET/CT correctly identified all patients with viable MZL and was superior to conventional staging (<i>P</i> < 0.001). CXCR4-directed imaging results were validated by confirmation of MZL in 16 of 18 PET-guided biopsy samples. Inclusion of CXCR4 PET/CT in primary staging significantly impacted staging results in almost half of patients and treatment protocols in a third (upstaging, <i>n</i> = 7; downstaging, <i>n</i> = 3; treatment change, <i>n</i> = 8; <i>P</i> < 0.03). <b>Conclusion:</b> CXCR4 PET/CT is a suitable tool in primary staging of MZL and holds the potential to improve existing diagnostic algorithms.