Enhancing prognostic accuracy in PMBCL: semiquantitative analysis of interim PET/CT scans

Primary mediastinal large B-cell lymphoma (PMBCL) is a rare, aggressive lymphoma affecting young adults. Interim PET/CT (iPET/CT) scans are used to assess treatment response, but the positive predictive value of standard Deauville score remains limited. This retrospective multicenter study analyzed 116 PMBCL patients treated with anthracycline-based chemoimmunotherapy, focusing on 90 patients with high quality iPET/CT. Semiquantitative radiomics metrics, including changes in maximum standardized uptake value (dSUVmax), metabolic tumor volume (dMTV), and total lesion glycolysis (dTLG), were assessed alongside event-free survival (EFS). All interim and final PET/CT scans were independently reviewed by two nuclear medicine physicians blinded to outcomes. Among the 90 patients, 62 (68.9%) were iPET-positive (Deauville scores 4-5). Event-free survival (EFS) at 3 years was significantly higher in iPET-negative patients compared to iPET-positive patients (75% vs. 29%; p < 0.01). Radiomics analysis demonstrated that dSUVmax, dMTV, and dTLG provided superior predictive accuracy for EFS. Values below optimized cut-off thresholds demonstrated significantly better outcomes (e.g., 3-y EFS: 77.8% for dSUVmax ≥ 80% vs. 11.1% for dSUVmax < 80%, p < 0.01). Radiomics-based metrics outperformed visual iPET/CT assessment in identifying high-risk patients, underscoring their potential in guiding treatment. Future research should integrate radiomics with clinical factors to enhance PET-guided treatment strategies.