Positron emission tomography/magnetic resonance imaging (PET/MRI) vs. gastroscopy: Can it improve detection of extranodal marginal zone lymphomas of the stomach following H. pylori treatment?

Abstract

Introduction: The stomach is the most common site of origin for extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma). Antibiotic eradication of Helicobacter pylori (H. pylori) is the standard first-line treatment, with response assessment being performed by histological evaluation of multiple gastric biopsies.

Areas covered: The objective of this review is to provide an update on results obtained using noninvasive methods, including magnetic resonance imaging (MRI), positron emission tomography combined with computed tomography (PET/CT), and most recently, PET/MRI for the assessment of disease extent and response to treatment in patients with gastric MALT lymphoma.

Expert opinion: While CT is the officially recommended imaging technique, few studies in small cohorts have suggested that diffusion-weighted MRI shows higher sensitivity, also relative to 18 F-FDG PET/CT, for both gastric and nongastric MALT lymphomas. A recent prospective study using PET/MRI with the novel CXCR4-targeting radiotracer 68 Ga-Pentixafor suggested that, for patients with gastric MALT lymphoma after H. pylori eradication, this imaging technique may provide excellent accuracy (97%) for assessment of residual or recurrent disease. Although recent studies on CXCR4-targeting PET and to some extent also diffusion-weighted MRI are promising, there is insufficient evidence to suggest a change in clinical practice.

Keywords: CXCR4 receptor; Extranodal marginal zone lymphoma; Helicobacter pylori; PET/MRI; gastroscopy; imaging.

Figure 1.

65-year-old patient with gastric MALT lymphoma at the greater curvature. While 18F-FDG-PET/CT shows only mild diffuse, non-specific FDG uptake, and CE-CT shows non-specific wall thickening that is difficult to interpret due to lack of distension, elevated signal on DWI (b800) and low signal on the ADC map suggest diffusion restriction, most prominently in its anterior portion (blue arrows), consistent with biopsy-proven lymphoma.

Figure 2.

61-year-old patient with gastric MALT lymphoma at the lesser curvature. While 68Ga-Pentixafor-PET/MRI shows obvious focal uptake at the site of the lesion (blue arrow), there is only subtle signal elevation on DWI (b800), and no correlate on the apparent diffusion coefficient (ADC) map. Morphological MRI using a T1-weighted Dixon sequence shows no distinct focal lesion, and only very mild gastric wall thickening at the site of the lymphoma.