Enhancing Prognostication and Treatment Response Evaluation in Primary CNS Lymphoma with 18F-FDG PET/CT.

Background: The role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in the prognostication and response evaluation of primary central nervous system lymphoma (PCNSL) remains inadequately defined.

Methods: We conducted a retrospective analysis of 268 consecutive newly diagnosed patients with PCNSL between 2006 and 2020. Of these patients, 105 and 110 patients were included to evaluate the prognostic value of baseline and post-treatment 18F-FDG-PET/CT scans, respectively. Tumor uptake was considered positive when it exceeded that of the contralateral brain upon visual assessment. Quantitative analysis of baseline 18F-FDG-PET/CT included measurement of the maximal standardized uptake value (SUVmax), total metabolic tumor volume (TMTV), and total lesion glycolysis (TLG).

Results: The median age of the 268 patients was 62 years (range: 17-85), with 55% being male. The median progression-free survival (PFS) was 24.5 months (95% confidence interval [CI], 19.9-29.1), and the median overall survival (OS) was 34.5 months (95% CI, 22.9-46.1). The average SUVmax was 15.3 ± 5.7 and the mean TMTV and TLG were 12.6 ± 13.9 cm3 and 135.0 ± 152.7 g, respectively. Patients with a baseline TMTV ≥17.0 cm3 had significantly shorter OS (12.5 vs. 74.0 months, p=0.011). Post-treatment metabolic response by 18F-FDG-PET/CT significantly predicted PFS (median: 10.5 vs. 46.0 months, p=0.001) and OS (median: 21.0 vs. 62.0 months, p=0.002), whereas anatomic response by contrast-enhanced MRI showed no statistically significant differences in PFS (p=0.130) or OS (p=0.540).

Conclusion: Baseline TMTV and post-treatment metabolic response, as assessed by 18F-FDG-PET/CT, are significant prognostic factors in patients with PCNSL.