TMIC-31. MOLECULAR PROGNOSTIC FACTORS OF THE PROGRESSION OF VESTIBULAR SCHWANNOMA AFTER PRIMARY TUMOR RESECTION

Abstract BACKGROUND Although vestibular schwannoma is a benign tumor, 10% of the tumor regrow after primary tumor resection. The factors associated with tumor progression from several reports remain controversial, and the role of the tumor microenvironment in vestibular schwannoma is still unclear. In this study, we analyzed the prognostic factors associated with the tumor progression after primary resection. METHODS We retrospectively reviewed the medical records of patients who underwent surgical resection and were diagnosed with vestibular schwannoma between January 2005 and June 2020. We performed RNA sequencing to identify the prognostic factors and immunohistochemistry to assess the tumor microenvironment, including analysis of the CD80 and CD206 expression of macrophages. We compared the progressed group whose tumor size got larger than 2mm after primary resection or who underwent additional treatment because of regrowth with the stable group. RESULTS Fifty-five patients underwent surgical resection for newly diagnosed vestibular schwannoma, and 12 of them had tumor regrowth. RNA sequencing revealed that the significantly upregulated pathways in the stable group was related to immune systems, while that of the progressed group was related to cell cycle. In addition, there were more myeloid cells, especially M2 macrophage infiltration in the stable group. Immunohistochemistry also showed higher M2 macrophages in the stable group. CONCLUSION In this study, multiomic analysis revealed the upregulation of immune-related pathways in the stable group and the cell cycle pathway in the progressed group. Altering the tumor microenvironment may offer a therapeutic strategy in vestibular schwannoma after primary resection.