Value of pretherapeutic DWI in evaluating prognosis and therapeutic effect in immunocompetent patients with primary central nervous system lymphoma given high-dose methotrexate-based chemotherapy: ADC-based assessment.

AIM: To investigate apparent diffusion coefficient (ADC) as a prognostic indicator in primary central nervous system lymphoma (PCNSL) by analysing patient clinical characteristics and pretherapeutic diffusion-weighted imaging (DWI).

MATERIALS AND METHODS: Clinical characteristics and pretherapeutic DWI were studied retrospectively in 28 patients receiving high-dose methotrexate (HD-MTX)-based chemotherapy. Mean (ADCmean), 95th percentile (ADC95%), and 5th percentile (ADC5%) ADC values of the enhancing tumour volume were measured. The influence of prognostic parameters on progression-free survival (PFS) was investigated by log-rank test and Cox regression analysis. Correlations between the variables and PFS or the level of Ki-67 expression were analysed. ADC and clinical features were analysed using an independent sample t-test between the complete response (CRi) and partial response (PRi) groups after initial four cycles of chemotherapy. Receiver operating characteristic (ROC) curves were constructed using ADC parameters.

RESULTS: Patients with CRi, lower Ki-67 level, higher Karnofsky performance status (KPS), ADC5%, or ADCmean showed better PFS. The level of Ki-67 expression and ADC5% were independent risk factors. There was a positive correlation between KPS, ADC5%, and PFS, and negative correlation between ADC5%, PFS, and the level of Ki-67 expression. There was a significant difference for PFS, KPS, ADCmean, and ADC5% between CRi and non-CRi; however, ADC5% outperformed ADCmean because the area under the ROC curve (AUC) using ADC5% (0.983) was higher than the AUC using ADCmean (0.822).

CONCLUSION: ADC measurements, especially ADC5%, are useful predictors for PFS and response to HD-MTX in PCNSL.