Introduction: Myxopapillary ependymomas (ME) are considered benign, slow-growing tumors. However recurrence, especially following incomplete resection, is known, with some tumors exhibiting malignant behavior. Unfortunately, most published series are small and of mixed histologic grade; we submit the largest series of MEs, focusing on treatment modality and outcome.

Methods: All 45 cases of pathologically confirmed Grade 1 ME from 2002-2010 were retrospectively reviewed focusing on surgical and radiation treatment and patterns of failure, 5 were excluded (<12 months follow-up, incomplete records). Patients were grouped based on surgical approach which was confirmed by both operative notes and pathology (en bloc/undisrupted capsule (EB), gross total resection (GTR), subtotal resection (STR)), and the use of postoperative radiotherapy (RT) vs none.

Results: Of the 40 patients (25 male, age average 38 (range 9-62)), 19 underwent EB without recurrence, 6 had GTR and 15 underwent STR. Kaplan-Meier survival curves are presented demonstrating a significant difference in tumor progression based on surgical approach (Fig1 EB/GTR/STR p= 0.005 and Fig2 EB/Other p=0.052). Progression of disease in patients with capsular violation (STR or GTR), the use of post-operative radiation (N=7) vs none (N=14) was not statistically significant (Fig 3, p=0.32), although sample size is small. Of the 11 patients with disease progression, 3 developed disease at a remote site; 2 were radiated postoperatively, however both recurrences were outside of the radiation port. Surgical complications were independent of surgical approach (2/19 EB: 1 CSF leak, 1 wound infection; 2/21 GTR/STR: 1 aseptic meningitis, 1 dysesthetic pain; p=1.0). However, postoperative bowel and bladder dysfunction was significantly more frequent in non-EB cases (EB: 0/19; GTR/STR: 8/21; p=0.0036).

Conclusions: Subtotal resection and tumor capsule violation increase the risk of recurrence of ME. Postoperative radiation may reduce the risk of recurrence in cases of tumor violation, but further study is indicated.

Patient Care: Our research underscores the importance of en bloc resection of myxopapillary ependymomas. Although subtotal resection has been demonstrated to increase likelihood of recurrence, we show that avoiding any capsular violation---including biopsy or piecemeal gross total resection---is decreases recurrence risk. Additionally, we demonstrate that capsular violation in the form of either subtotal or gross total resection increases the risk of iatrogenic neurologic injury in the form of cauda equina dysfunction. Finally, the use of radiation in postoperative capsular violations is discussed. We look forward to expanding our series retrospectively.

Learning Objectives: 1. Discuss the difference in surgical technique between EB/GTR/STR and why this is important 2. Discuss the role of postoperative radiation in cases of capsular violation 3. Discuss surgical risk based on operative technique

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