Brain Metastases and their surrounding edema: a Descriptive Study

Background and Purpose: We found no prior reports on the relationship of brain metastases and their corresponding edema size. We aim to identify 1) a general threshold for the occurence of edema and 2), for clinical purposes, brain regions where edema rarely occur. Materials and Methods: This is a monocentric, retrospective, study including 51 patients with 335 histologically proven (or highly suspicious) brain metastases in whom an MRI scan was performed in 01/2009-05/2015. Volumetry on contrast-enhanced T1w and T2w/ FLAIR was performed for all metastases and edemas, respectively. ROC analysis and Chi2 test were used for statistical testing. Results: Tumor types were as follows: pulmonary cancer (n = 28/125 metastases), skin (n = 11/117), breast (n = 4/24), genitourinary (n = 5/25), gastrointestinal (n = 1/1), and CUP (n = 2/43). A diameter of 0.55 cm (AUC 0.86, accuracy 0.81) best separated patients with and without edema (p < 0.001). There was no significant difference in the location of metastases and the occurence of edema. Conclusion: Brain metastases over 0.55 cm in diameter may be easier to identify on imaging due to the higher probability of presence of surrounding edema. In a lesion