ANGI-11. SEX DIFFERENCES IN SOX2 GLIOBLASTOMA EXPRESSION OUTSIDE MRI-DEFINED CONTRAST ENHANCEMENT AT AUTOPSY

Abstract INTRODUCTION Sex-determining region Y-box 2 (SOX2) has recently been used as a marker for pluripotency to identify cellular glioblastoma invasion pathologically. This can be used to identify areas of tumor invasion consisting of sparse individual cells, likely highlighting the furthest margin of tumor invasion. This study aligned large format SOX2 stained tissue samples to conventional MRI to determine demographic factors that impact the presence of SOX2 positive invasion outside the T1 contrast-enhanced tumor margin. METHODS The cohort for this study consisted of 36 IDH-wildtype glioblastoma patients (23 male, 13 female, mean age=61.9). Tissue samples from areas of suspected tumor invasion and normal tissue were collected at autopsy, stained for SOX2, digitized at 40X resolution, and automatically segmented for SOX2 positive staining cell percent (SOX2+%) at MR resolution using a color deconvolution algorithm. Contrast enhanced T1 scans from acquisitions close to death were annotated manually for tumor presence and aligned to the T2-weighted FLAIR image. Tissue data was then aligned to MR images using a custom in-house software that relies on manually defined control points to generate a nonlinear transform that warps tissue into MR space while correcting for tissue shrinkage. Mean SOX2+% was computed for each patient outside of contrast enhancement and compared across age and sex as demographic factors. RESULTS Males were found to have a higher SOX2+% than females outside contrast enhancement (t=2.09, p=0.045), while no association with age was observed (r=0.146, p=0.397). CONCLUSIONS Sex differences were observed for non-enhancing SOX2 positivity, which may relate to the more aggressive tumors identified in male patients in some studies. Further research into the mechanisms behind sex differences in tumor growth patterns and molecular characteristics impacting the infiltration of tumor beyond the MR defined region is needed.