GE-06 * PROGNOSTIC SIGNIFICANCE OF RELATIVE 1p19q CODELETION IN OLIGODENDROGLIAL TUMORS

Abstract

BACKGROUND: 1p19q codeletion is a favorable prognostic marker for oligodendroglial tumors (OT) that in anaplastic OT is as well predictive of good response to radiotherapy and alkylator chemotherapy. OBJECTIVE: Assess outcome in relative 1p19q codeleted OT defined as the presence of both polysomy and 1p19q codeletion. METHODS: Between the years 2001-2013, 525 cases were examined at the University of Washington by dual color FISH for 1p or 19q deletion. 437 (82%) were WHO Grade 2 or 3 OT of which 209 (48%) were 1p19q codeleted. 72 (16%) were relatively deleted for either one or both 1p and 19q of which 28 (6%) were relatively 1p19q codeleted. RESULTS: Median overall survival was as follows. WHO Grade 2 OT (n = 296): 1p19q codeleted (n = 155) 13+ years; uni- or nondeleted (n = 86) 5+ years; relative deletion for one or both 1p19q (n = 41)) 6+ years; and relative 1p19q codeletion (n = 15) 6+ years. WHO Grade 3 OT (n = 168): 1p19q codeleted (n = 54) 11+ years; uni- or nondeleted (n = 70) 2.5 years; relative deletion for one or both 1p19q (n = 31)) 3 years; and relative 1p19q codeletion (n = 13) 4+ years. CONCLUSIONS: Median overall survival for OT either WHO Grade 2 or 3 with relative codeletion of 1p19q were approximately one half that of 1p19q codeleted tumors. The presence of relative codeletion, operationally defined as polysomy with deletions, is of prognostic significance.