IMG-57. A probabilistic atlas for the spatial distribution of CNS metastases in the posterior fossa based on primary site of origin

Emerging evidence in CNS metastases has captured direct influences of the primary tumor on the microenvironment and its eventual metastatic destination. En masse interrogation of large datasets have revealed a predilection for different anatomical locations based on primary tumor type. Despite the unique clinical and surgical considerations of posterior fossa lesions, no studies have specifically explored the landscape of metastases to the posterior fossa. To create a posterior fossa-specific atlas of predilections for CNS metastases based on primary tumor type. A retrospective study was performed at a single institution (University of Minnesota Medical Center) from August 2005 to December 2022. A large database of stereotactic surgery-treated lesions was analyzed and their clinical demographics obtained (age, gender, treatment date, primary tumor type). T1-weighted post-contrast images containing lesions were mapped to a template brain. Posterior fossa lesions were subsetted by calculating lesion centroids in template-space and assessing if they were in the posterior fossa. 1537 posterior fossa lesions were identified from 520 unique patients (302 females, 217 male, 1 unknown). Primary tumor types included were: breast (603 lesions), Lung-NSCLC (354 lesions), Melanoma (181 lesions), Lung-SC (145 lesions), Renal (97 lesions), Colorectal (56 lesions), Ovarian (44 lesions), Bladder (14 lesions). Breast lesions showed a left sided preference. Colorectal lesions appeared closer to midline (vermian and slightly paravermian). Conversely, lung (non-small cell) lesions appeared the furthest from midline. Renal lesions also appeared more vermian, with a significant portion involving the brainstem. CNS metastatic lesions to the posterior fossa follow a primary tumor type-specific probabilistic atlas.