Improved primary staging of marginal zone lymphoma by addition of CXCR4-directed PET/CT

Abstract

Positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodesoxyglucose (FDG) is an integral component in the primary staging of most lymphomas. However, its utility is limited in marginal zone lymphoma (MZL) due to inconsistent FDG avidity. One diagnostic alternative could be the targeting of CXC-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. Methods: 22 newly diagnosed MZL patients were staged conventionally and with ⁶⁸Ga-Pentixafor PET/CT. Lesions exclusively identified by ⁶⁸Ga-Pentixafor PET/CT were biopsied as standard of reference and compared to imaging results. The impact of CXCR4-directed imaging on staging results and treatment protocol was assessed. Results: ⁶⁸Ga-Pentixafor PET/CT correctly identified all patients with viable MZL and was superior to conventional staging (P < 0.001). CXCR4-directed imaging results were validated by confirmation of MZL in 21/24 PET-guided biopsy samples. Inclusion of ⁶⁸Ga-Pentixafor PET/CT in primary staging significantly impacted staging results in almost half, and treatment protocols in one third of patients (upstaging, n = 7; downstaging, n = 3; treatment change, n = 8; P < 0.03). Conclusion: ⁶⁸Ga-Pentixafor PET/CT is a suitable tool in primary staging of MZL and holds the potential to improve existing diagnostic algorithms.