Non-invasive evaluation of CXCR4 expression of MALT lymphoma using ⁶⁸Ga-Pentixafor PET/MRI- a prospective study

Objectives: MALT lymphomas are a challenge for non-invasive diagnosis. So far, biopsy is still needed for staging and re-staging. MALT lymphoma express the chemokine receptor CXCR4 on a regular basis, and 68Ga-Pentixafor has shown to quantify CXCR4 expression non-invasively . Based on these findings, we evaluated for the first time 68Ga-Pentixafor PET/MRI for non-invasive diagnosis of MALT lymphoma.

Methods: This study was approved by the local ethical committee. We prospectively included 14 patients with MALT lymphoma in this study (7 male, age 69). Localisations were stomach (n=4), lung (n=2), liver (n=1), kidney (n=2), skin (n=1), tonsils (n=1), bladder (n=1) and orbita (n=2). Precursor for ⁶⁸Ga-Pentixafor synthesis was provided by Scintomics in GMP grade. 60 minutes after application of mean 172 MBq ⁶⁸Ga-Pentixafor whole-body PET images were acquired with 5 minutes per bed position. Simultaneously the following MRI sequences were acquired: axial T1 vibe Dixon, coronal T2 haste, axial diffusion weighted images (ADC, b_50, b_800). We evaluated the uptake (SUVmax, SUVmean, SUVpeak) and volume in MALT lymphoma and the SUVmax of the liver as background. All MALT lymphomas were verified by biopsy.

Results: In all patients the MALT lymphoma showed increased uptake of ⁶⁸Ga-Pentixafor. Mean SUVmax was 10.8 (range 4.1-25.4), SUVmean 5.5 (range 2.9-10.2), and SUVpeak 10.3 (range 7.1-22.7; 2 patients with low tumor volume were not evaluable). The mean SUVmax of the liver was 1.8. The tumor-to-background ratio was excellent with mean 5.8 (range 2.4-14.9). The mean tumor volume was 94.3 ml (range 3.4-306).

Conclusion: In this study all MALT lymphoma had high ⁶⁸Ga-Pentixafor uptake with excellent tumor-to-background ratios, therefore, enabling non-invasive diagnosis. Research Support: Scintomics GmbH