Imaging of chemokine receptor-4 targeted PET/CT with 68Ga-Pentixafor in lymphoma: comparison to 18F-FDG

167 Objectives: Positivity of chemokine receptor-4(CXCR4)-targeted PET with 68Ga-Pentixafor had been observed in malignancies. The aim of this prospective study was to describe the imaging of CXCR4 in a spectrum of patients with various types of lymphoma. Methods: 27 patients (18 M, 9 F; 58.1±13.6y, 15-87y) diagnosed with lymphoma and naive of therapy were recruited prospectively. All patients underwent 68Ga-Pentixafor and FDG PET/CT with routine procedures. All PET scans were visually rated as positive or negative. Visually, the tracer depicting higher number or intensity of lesions was considered superior. Semi-quantitative analysis was performed with tumor-to-background ratios (TBR). Tumor uptakes were defined as SUVmax of the most avid lesion. The left ventricle was referred as the background. Results: Clinical Characteristics The lymphomas of the 27 enrolled patients included lymphoplasmacytic lymphoma(LPL)(7), marginal zone lymphoma(MZL)(5), diffuse large B cell lymphoma(DLBCL)(4), T-cell lymphoma (3), unspecific indolent B-cell lymphoma (3), follicular lymphoma(FL)(2), NK/T cell lymphoma (2), and mantle-cell lymphoma(MCL) (1). 88.9%(24/27) of the patients were stage IV. The tumor involved lymph nodes and bone marrow (both 14/27) most commomly. Clinical characteristics are given in Table 1. Imaging Results:68Ga-Pentixafor was visually rated positive in 25/27 subjects (92.6%), whereas FDG was positive in 23/27 (85.2%). TBR with 68Ga-Pentixafor and FDG were 4.5±3.9 and 4.8±4.8, respectively. LPL 68Ga-Pentixafor were positive and superior over FDG in all patients with LPL. 4/7 patients were positive both in 68Ga-Pentixafor and FDG, but 68Ga-Pentixafor showed higher intensity of uptake and more extensive scope of disease (Figure 1A). Especially, 68Ga-Pentixafor was better in detecting disease of lymph nodes and other extramedullary disease. The remaining 3/7 patients were CXCR4+/FDG-. MZL All 5 patients with MZL were CXCR4+/FDG+. 68Ga-Pentixafor was superior to FDG in 2/5 patients with higher intensity (Figure 1B) and additional positive findings in meninge. Two tracers were comparable in 2/5 patients with disease in lung, pleura, peritoneum and bone marrow.In the remaining 1 patient, FDG showed higher trace-avidity in lymph nodes and bone marrow . Unspecific indolent B-cell lymphoma 68Ga-Pentixafor and FDG were concordantly positive and comparable in 3/3 patients with similar tracer uptake and disease extention. DLBCL68Ga-Pentixafor and FDG were both positive in 4/4 patients. But 68Ga-Pentixafor yielded inferiority to FDG of intensity in 3 of them. In the remaining 1 patient, two tracers showed similar tracer uptake and involvement. FL 68Ga-Pentixafor and FDG were comparable in one patient. However in the other patient, lesions in lymph nodes, spleen and bone showed more intense uptake of FDG than 68Ga-Pentixafor (Figure 1C). MCL In the only one patient, 68Ga-Pentixafor was inferior to FDG with similar involvement but lower intensity. T-cell lymphoma68Ga-Pentixafor showed no superiority to FDG.1/3 patient was CXCR4+/FDG+ with comparable results of intensity and involvement, 1/3 was CXCR4-/FDG- and 1/3 was CXCR4-/FDG+. NK/T celllymphoma FDG showed superiority in both two patients either with higher intensity or more extensive involvement in lymph nodes, subcutaneous area and nasal cavity. Visual comparison of two tracers in different types was given in Figure 2. In semi-quantitative analysis ,TBR of CXCR4 in LPL was significantly higher than those of FDG (p=0.006). Comparison of TBR in the remaining types were given in Table 2. Conclusions: 68Ga-Pentixafor showed superiority to FDG in all patients with LPL. In most of the patients with MZL, 68Ga-Pentixafor was superior to FDG. In aggressive lymphoma, 68Ga-Pentixafor were positive in all patients but with relatively lower tracer-uptake comparing to FDG. 68Ga-Pentixafor had highestly negative rate in T-cell lymphoma, and it was also inferior to FDG in NK/T cell lymphoma.