Primary Central Nervous System Lymphoma (PCNSL) is a highly malignant brain tumour. We investigated dynamic changes in tumour volume and apparent diffusion coefficient (ADC) measurements for predicting outcome following treatment with MATRix chemotherapy in PCNSL. Patients treated with MATRix (n = 38) underwent T1 contrast-enhanced (T1CE) and diffusion-weighted imaging (DWI) before treatment, after two cycles and after four cycles of chemotherapy. Response was assessed using the International PCNSL Collaborative Group (IPCG) imaging criteria. ADC histogram parameters and T1CE tumour volumes were compared among response groups, using one-way ANOVA testing. Logistic regression was performed to examine those imaging parameters predictive of response. Response after two cycles of chemotherapy differed from response after four cycles; of the six patients with progressive disease (PD) after four cycles of treatment, two (33%) had demonstrated a partial response (PR) or complete response (CR) after two cycles. ADC_mean at baseline, T1CE at baseline and T1CE percentage volume change differed between response groups (0.005 < p < 0.038) and were predictive of MATRix treatment response (area under the curve: 0.672–0.854). Baseline ADC and T1CE metrics are potential biomarkers for risk stratification of PCNSL patients early during remission induction therapy with MATRix. Standard interim response assessment (after two cycles) according to IPCG imaging criteria does not reliably predict early disease progression in the context of a conventional treatment approach.

Introduction: Despite treatment advances, accurate prognostication for patients with newly diagnosed primary central nervous system lymphoma (PCNSL) remains unsatisfactory. This retrospective cohort study evaluated whether T1 contrast-enhanced (T1CE) tumour volume and apparent diffusion coefficient (ADC) metrics on magnetic resonance imaging (MRI) predict survival in PCNSL patients treated uniformly with MATRix chemotherapy. Methods: Sixty-five patients underwent pre-treatment MRI with volumetric and diffusion analysis. T1CE tumour volume, ADCmean, ADCmin and normalised diffusion parameters were assessed. Survival outcomes were analysed using univariate Cox regression for overall survival (OS) and progression-free survival (PFS), including disease-specific endpoints. Results: None of the tested imaging variables were significantly associated with OS or PFS, including T1CE tumour volume and ADC measures. Baseline T1CE and diffusion biomarkers did not predict survival in MATRix-treated PCNSL. Discussion: These results highlight limitations of standard MRI techniques for prognostication underscoring the need for integrated multiparametric models incorporating imaging and biological data to improve outcome prediction.