Clinical and pathological predictors for FDG-PET/CT avidity in patients with marginal zone lymphoma—a retrospective cohort study

Background: The clinical value of FDG-PET/CT for staging and monitoring treatment response in patients with aggressive lymphoma is well established. Conversely, its role in the assessment and management of marginal zone lymphoma (MZL) is less conclusive. We aimed to assess clinical, laboratory, and pathological predictors for FDG uptake in these patients, in an attempt to identify MZL patients whose management will benefit from this imaging modality. Methods: In this single-center, retrospective cohort study, we included all adult patients diagnosed with MZL at the Rabin Medical Center between January 2006 and December 2020 who underwent FDG-PET/CT at the time of diagnosis. Primary outcomes were FDG avidity (defined as a visual assessment of at least moderate intensity), SUVmax, and SUVliver. Variables such as advanced clinical stage, primary disease site, hemoglobin level (Hb), platelet count (Plt), serum albumin, LDH level, β-2 microglobulin, and Ki 67 index were evaluated univariate and multivariate analysis using logistic and linear regression models. Association between FDG avidity and progression-free and overall survival was evaluated using Kaplan–Meier curves and Cox regression analysis. Results: A total of 207 MZL patients were included in this study, 76 of whom (36.7%) had FDG-avid disease. Baseline patients’ characteristics such as age, gender, and comorbid conditions were similar between patients with and without significant FDG uptake. In a multivariate logistic regression model, non-gastric MALT (OR 4.2, 95% CI 1.78–10), Ki 67 index ≥ 15% (OR 3.64, 95% CI 1.36–9.76), and elevated LDH level (OR 8.6, 95% CI 3.2–22.8) were all associated with positive FDG avidity. In a multivariate linear regression model, a combination of advanced clinical stage, specific disease subtypes, LDH level, and Ki 67 index predicted the value of SUVmax (P value < 0.001; adjusted R² = 33.8%) and SUVmax/SUVliver (P value < 0.001; adjusted R² = 27%). Baseline FDG avidity was associated to PFS and OS only in univariate analyses. Conclusions: In this retrospective cohort study, we present prediction models for positive FDG uptake and SUVmax in MZL patients. These models aim to help clinicians choose patients suitable for incorporation of FDG-PET/CT for staging and monitoring disease and reduce the costs of redundant tests.