Introduction:
Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive non-Hodgkin lymphoma in adults. Bone marrow infiltration (BMI) in DLBCL indicates advanced disease and impacts prognosis and treatment decisions. While bone marrow biopsy (BMB) is the traditional gold standard for detecting BMI, 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has emerged as a noninvasive alternative. This study aimed to compare the diagnostic performance of 18F-FDG PET/CT and BMB in detecting BMI and to evaluate the prognostic significance of several volumetric PET parameters and the International Prognostic Index (IPI) for treatment outcomes in DLBCL.
Methods:
This retrospective cohort included 145 patients with newly diagnosed DLBCL stage II-IV who underwent both baseline 18F-FDG PET/CT and BMB between 2016 and 2020. PET images were assessed semi-quantitatively and volumetrically, including maximum standardized uptake value (SUVmax), and metabolic tumor volume (MTV), using 3D Slicer software. BMI was considered present if PET showed focal/multifocal uptake exceeding hepatic activity and was confirmed by treatment response or BMB. For volumetric analyses, a threshold of SUV ≥ 4.0 g/ml was used. Prognostic values of PET parameters for complete remission after systemic therapy (iCR) and overall survival (OS) were evaluated using Kaplan-Meier, ROC analysis, logistic regression, and Cox proportional hazards models. Prognostic values of PET-derived biomarkers were compared to the clinical parameters, including IPI.
Results:
PET/CT detected BMI in 26.2% of patients, compared to 12.4% with BMB. PET/CT demonstrated higher sensitivity (88.4% vs. 41.9%) and accuracy (96.5% vs. 61.5%) than BMB. iCR was achieved in 56% of patients. Significant predictors of iCR included total disease MTV, extra-marrow MTV, PET positive bone marrow, IPI, and disease stage. For 3-year OS (OS3), significant predictors included IPI, WHO performance status, disease stage, as well as total and extra-marrow MTV. In contrast, 5-year OS (OS5) was associated only with IPI and its clinical components. IPI remained the strongest predictor of both OS3 and OS5. Although volumetric PET parameters were significant in univariate analyses, their prognostic impact diminished in multivariate models including IPI. Interestingly, SUVmax of BM lesions was inversely associated with mortality in the uni- and multivariate analysis.
Conclusions:
18F-FDG PET/CT outperforms BMB in sensitivity and diagnostic accuracy for detection of BMI in DLBCL. While volumetric PET biomarkers provide valuable prognostic information for early treatment response and short term survival, IPI remains the dominant long term predictor. PET based BM metrics, when interpreted in clinical context, may facilitate prognostic assessments and treatment optimisation.
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