P16.25 Surgical resection and cellular proliferation predict prognosis for papillary glioneuronal tumor

Abstract Object: The World Health Organization classifies papillary glioneuronal tumor (PGNT) as Grade I, however, several malignant cases have been reported. PGNT is a rare brain tumor that occurs in the white matter and affects young adults. The purpose of this study was to establish the clinical characteristics of this unfamiliar entity. Methods: PubMed/NCBI was queried for patient-level reports of PGNT, resulting in 132 cases. Six additional cases treated at Brigham & Women’s Hospital and Massachusetts General Hospital were assessed for a total of 138. A Kaplan-Meier and Cox regression analyses were conducted to determine predictors of progression-free survival (PFS). Results: PGNT has a higher prevalence in males (1.4:1), and presents at age 27.1 ± 16.4 (SD). Presenting symptoms include headache (64%) and seizure (37.8%), with a mean duration of 13.3 months. Average radiological size is 4.3 cm. Common locations of occurrence were frontal (32.1%) and temporal (22.4%) lobes. Tumors were periventricular (48.2%, effacing), proximal to a ventricle (20%, <1.0 cm) and intraventricular (11.8%). They were commonly cystic/solid (39.8 percent). Tumors often demonstrated calcification (47.7%) and edema (45.5%). Enhancement on magnetic resonance imaging showed a heterogeneous (32%) or ring pattern (25.2%). The average Ki-67 index of proliferation was 3.6, with six cases greater than 10. Treatment included gross-total resection (GTR), subtotal resection (STR), and adjuvant radiation, chemotherapy or both. Five years post-treatment, PGNT had an 85.1 PFS rate (95% CI:75.2-91.2). In patients treated with surgery alone, PFS was higher after GTR compared to after STR (Mantel-Cox analysis, p<0.0001). Cox regression analysis demonstrated that recurrence is nearly 10 times more likely after STR than after GTR (p<0.001). A Ki-67 index less than 5 percent resulted in a greater PFS than an index greater than 5 percent (p<0.001). Conclusion: PGNT is a benign tumor, but can present atypically as high-grade. GTR is the most common treatment, and cases can warrant radiation and chemotherapy. Maximal surgical resection and cellular proliferation are prognostic indicators for PGNT. This study represents the most comprehensive clinical understanding of this rare tumor. More research is needed to evaluate the diverse presentation of PGNT.