IMG-64. Baseline imaging metrics stratifying progression-free survival and overall survival in primary central nervous system lymphoma treated with high-dose methotrexate

Abstract BACKGROUND First-line therapy for primary central nervous system lymphoma (PCNSL) typically incorporates high-dose methotrexate. Despite high response rates (40-70%), a subset of patients (20-40%) progress during or after induction therapy. This study evaluates the performance of conventional, diffusion, and perfusion imaging as non-invasive biomarkers to predict progression-free survival (PFS) and overall survival (OS). METHODS Eighty-five immunocompetent patients with histologically-proven PCNSL, who received first-line methotrexate, and with available pre-treatment MRI were retrospectively identified. PCNSL contrast-enhancing and non-enhancing lesion components were segmented using conventional MRI, to extract the following MRI metrics: contrast-enhancing tumor volume, whole-lesion volume, median apparent diffusion coefficient (ADC) and median relative cerebral blood volume (rCBV) of the contrast-enhancing tumor. Multivariate survival analyses were conducted with Cox models, and univariate analyses on categorical variables with log-rank. RESULTS Final results will be presented at the meeting. In a preliminary sub-cohort of twenty-seven patients, progressive disease (PD) occurred in n=8 patients, either during (n=5) or after induction (n=3). After adjusting for age and sex, the pre-treatment contrast-enhancing tumor volume was an independent predictor of PFS (p=0.038, HR=1.10, 95%C.I.=1.02–1.18), the whole lesion volume showed a trend towards predicting PFS (p=0.073, HR=1.02, 95%C.I.=1.00–1.03), whereas baseline ADC and rCBV did not. A three-group categorization based on pre-treatment age and contrast-enhancing volume (<70 years <10 cc, vs. >70 years or >10 cc, vs. >70 years and >10 cc) successfully stratified PFS (p=0.023), with PFS probability at 3 years: 100%, 72%, and 25%, in the three groups, respectively. PD occurrence predicted OS (p=0.004), with OS probability at 3 years: 75% without PD vs. 29% with PD. CONCLUSION Comprehensive analyses on the entire cohort will be presented at the meeting, and will more thoroughly test both pre-treatment MRI metrics and pre-to-post-treatment MRI changes as PFS and OS predictors, while accounting for clinical covariates and treatment schemes.