The Diagnostic Value of the Apparent Diffusion Coefficient Values Derived from Magnetic Resonance Imaging and Diffusion-Weighted Imaging in Differentiating the Types of Metastatic Brain Tumors

Background: In brain metastatic lesions, peritumoral edema assessed by advanced imaging modalities is reported to have infiltration by neoplastic cells; however, determining the tumor border is still inaccurately depicted even by applying such modalities. More importantly, the apparent diffusion coefficient (ADC) values of this area for predicting tumor-related characteristics such as diametric and morphologic characteristics of lesions, as well as their primary source, remain uncertain. Objectives: In the current study, we aimed at assessing the value of ADCs in both intratumoral and peritumoral areas to determine the metastatic brain tumor source and to predict the morphological characteristics of the tumor. Methods: This study was conducted on 80 biopsy-proven patients with brain metastasis and underwent magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) examination. All tumor characteristics including the number and size of lesions, the origin of metastasis, the zone of metastasis, and the presence of necrosis or edema in the lesions were collected based on imaging. The origins of the metastasis were also determined. Results: The ADCmin and ADCmean values of the peritumoral area were strongly associated with the grade of edema in this area; however, none of the values could accurately predict the origin of metastasis. Determining the ADCmin and ADCmean in the intratumoral area could not be indicators for lesion characteristics such as size and location of the lesion, the presence of necrosis or edema, as well as the source of the metastatic tumor such as breast or lung. Similarly, the ADCmin and ADCmean in the peritumoral area could not be an effective predictor for determining the source of metastasis and also diameter, location, or necrotic nature of the tumor and only can predict the edematous pattern of the lesion. Conclusions: The ADC values in both intratumoral and peritumoral areas of the brain tumor metastatic lesion may not be predictive for the assessment of tumor morphology or its origin.