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 (ADC(mean)), 95th percentile (ADC(95%)), and 5th percentile (ADC(5%)) 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), ADC(5%), or ADC(mean) showed better PFS. The level of Ki-67 expression and ADC(5%) were independent risk factors. There was a positive correlation between KPS, ADC(5%), and PFS, and negative correlation between ADC(5%), PFS, and the level of Ki-67 expression. There was a significant difference for PFS, KPS, ADC(mean), and ADC(5%) between CRi and non-CRi; however, ADC(5%) outperformed ADC(mean) because the area under the ROC curve (AUC) using ADC(5%) (0.983) was higher than the AUC using ADC(mean) (0.822). CONCLUSION: ADC measurements, especially ADC(5%), are useful predictors for PFS and response to HD-MTX in PCNSL. (C) 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.