A preliminary evaluation of [¹⁸F] FDG and [¹⁸F] AlF-NOTA-Pentixafor PET/CT in gastric MALT lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is an indolent B-cell neoplasm with variable uptake on [¹⁸F] FDG PET/CT, limiting its clinical utility. [¹⁸F] AlF-NOTA-Pentixafor ([¹⁸F] Pentixafor), a novel PET tracer targeting the chemokine receptor CXCR4, may serve as an alternative imaging option. This preliminary study compared the detection performance of both tracers for gastric MALT lymphoma lesions and identified factors associated with [¹⁸F] Pentixafor PET/CT positivity. Twenty patients (11 male and 9 female) with pathologically confirmed gastric MALT lymphoma underwent both [¹⁸F] FDG and [¹⁸F] Pentixafor PET/CT scans. The McNemar test compared detection rates of the tracers, and semiquantitative parameters like SUVmax, SUVmean, and tumor-to-blood pool ratio (TBR) were assessed for gastric and extragastric lesions. A univariate analysis was performed to identify clinical factors associated with [¹⁸F] Pentixafor PET positivity. The [¹⁸F] Pentixafor PET/CT scan was positive in 9 out of 20 gastric lesions (45%), compared to 4 out of 20 (20%) for the [¹⁸F] FDG PET/CT. The median SUVmax for Pentixafor-positive gastric lesions was 4.2 (range 1.1–7.2). Among five patients with extragastric disease, [¹⁸F] Pentixafor uptake was numerically higher in extragastric than in gastric lesions, whereas [¹⁸F] FDG showed no consistent pattern. Pooled lymph-node and pulmonary lesions also showed higher [¹⁸F] Pentixafor uptake than [¹⁸F] FDG. CT gastric wall abnormality was significantly associated with positive Pentixafor PET/CT findings ( P < 0.001), while age, sex, Lugano classification, and Ki-67 index showed no significant associations. All semiquantitative data are descriptive, and direct comparisons between tracers were not performed due to the small and non-matched sample. In this exploratory cohort study, [¹⁸F] Pentixafor PET/CT detected more gastric lesions than [¹⁸F] FDG, but the difference was not statistically significant. Positive Pentixafor uptake was associated with CT-visible gastric wall abnormalities, though its added benefit over CT alone was limited. These preliminary findings require further investigation in larger studies to define the clinical role of [¹⁸F] Pentixafor PET/CT in gastric MALT lymphoma.