Quantitative 18F-FDG-PET/CT analysis of splenic suvmax enhances diagnostic accuracy in primary splenic non-Hodgkin lymphoma

Abstract Introduction Primary splenic Non-Hodgkin lymphoma (PS-NHL) is an uncommon extranodal lymphoma, representing less than 1% of all lymphomas, and is often diagnosed at an advanced stage due to nonspecific symptoms. Accurate differentiation between aggressive and indolent subtypes is crucial for guiding treatment and predicting outcomes. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has emerged as an important imaging modality in lymphoma evaluation. This study aimed to investigate the clinical characteristics, pathological subtypes, treatment strategies, and survival outcomes of PS-NHL, with particular emphasis on the diagnostic utility of splenic maximum standardized uptake value (SUVmax) in distinguishing aggressive disease. Methods 90 consecutive patients with PS-NHL diagnosed by splenic biopsy or splenectomy at the First Affiliated Hospital of Zhejiang University School of Medicine between March 2011 to December 2024 were retrospectively analyzed. Exclusion criteria included prior lymphoma, extra-splenic involvement beyond Ahmann stage III, or insufficient follow-up. Patients were categorized into aggressive or indolent subtypes based on histopathology. Baseline demographics, clinical presentation, laboratory results, imaging features, treatment regimens, and survival data were collected. 18F-FDG PET/CT was performed in most patients, and splenic SUVmax was measured. Receiver operating characteristic (ROC) analysis was used to determine the optimal SUVmax threshold for predicting aggressive histology. Survival outcomes were analyzed using the Kaplan–Meier method, and prognostic factors were assessed using Cox proportional hazards regression. Results The median age was 59 years, and 48.8% were male. Aggressive subtypes predominated, with diffuse large B-cell lymphoma (DLBCL) accounting for 65.5% (59/90). Common symptoms included abdominal pain and distension. All patients underwent ultrasound, CT, and 18F-FDG PET/CT, which demonstrated splenomegaly or splenic lesions without superficial lymphadenopathy. Ultrasound/CT identified focal splenic lesions in 66.2% (n=45/68) of aggressive PS-NHL compared to diffuse splenic involvement in 59.1% (n=13/22) of indolent PS-NHL. The median SUVmax on 18F-FDG PET/CT was significantly higher in aggressive than indolent cases (14.6 vs. 6.0, P = 0.004). ROC curve analysis determined an optimal SUVmax cutoff of 6.7 for predicting aggressive disease (area under the curve [AUC] = 0.77; sensitivity 62.5%; specificity 92.3%). Treatment groups included splenectomy alone (S, n=13) splenectomy followed by chemotherapy (SC, n=45) and chemotherapy alone (C, n=32).In aggressive PS-NHL, Ahmann stage III patients had a lower overall response rate (ORR) compared with stage I+II (53.3% vs. 89.5%, P = 0.013). Among stage III patients, OS was significantly longer in the SC group compared with the C group (67.4 vs. 10.4 months, P = 0.033). In indolent PS-NHL, median survival was not reached in any treatment group. Overall, aggressive PS-NHL had worse prognosis than indolent (5-year OS 58.1% vs. 85%, P = 0.012; 5-year progression-free survival [PFS] 51.6% vs. 80%, P = 0.008). Within aggressive subtypes, Ahmann stage III had inferior OS and PFS compared with stage I+II (OS P = 0.001; PFS P = 0.004), and SC improved outcomes in stage III compared with C. Conclusions PS-NHL typically presents with abdominal symptoms, most commonly DLBCL. A splenic SUVmax ≥6.7 on 18F-FDG PET/CT predicts aggressive histology with high specificity. In aggressive PS-NHL, Ahmann stage III is associated with poorer outcomes, and splenectomy followed by chemotherapy provides significant survival benefit over chemotherapy alone. Indolent PS-NHL can achieve durable survival with splenectomy. SUVmax measurement by 18F-FDG PET/CT may serve as a practical noninvasive biomarker to aid in risk stratification and treatment decision-making.