[1728] 1p/19q Co-Deletion and Polysomy in Oligodendroglial Tumors – A Single Institution Study

Hui Chen, Comer Stewart, Rosenblum Marc, Huse Jason, Wang Lu, Jhanwar Suresh, Nafa Khedoudja, Hameed Meera. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: The allelic loss of 1p and 19q in oligodendroglial tumors is mediated by the formation of the balanced translocation involving chromosomes 1 and 19 with subsequent loss of the derivative chromosome der (1; 19) (p10; q10) and maintenance of the der (1; 19) (q10; p10). While this observation and subsequent data has clearly shown a survival advantage and response to therapy in these tumors, the co-existence of the other changes such as polysomy and its outcomes have only been explored in very few studies. In this study we retrospectively analyzed the FISH patterns of 1p/19q co-deletion in oligodendroglial tumors.
Design: We collected pathological data and FISH results on oligodendroglial tumors during 2007 to 2010 from database of Pathology Department at Memorial Sloan-Kettering Cancer Center. Eighty-two patients with 1p/19q co-deletion were identified. There were 37 males and 45 females. Forty-eight cases were WHO Grade II oligodendrogliomas and thirty-four tumors were WHO grade III/anaplastic oligodendrogliomas.
Results: In this group of eighty-two 1p/19q co-deleted oligodendrogliomas, 17 cases showed in addition polysomy for 1p and/or19q (21%). Of the forty-eight WHO grade II tumors, 42 (87.5%) showed standard co-deletion (SCOD) and six showed co-deletion with polysomy (12.5%). Of the thirty-four WHO grade III tumors, 23 (68%) showed SCOD and eleven showed co-deletion with polysomy (32%).The mean age in both groups (Polysomy with co-deletion and SCOD) were 48 years and 42 years respectively. MGMT methylation was performed on thirty one patients. Sixteen out of 21 (76%) patients with SCOD showed MGMT methylation whereas all ten patients with co-deletion and polysomy showed MGMT methylation.
Conclusions: 1) In Oligodendrogliomas with co-deletion of 1p/19q, polysomy is seen in 20% of cases
2) Polysomy is seen 65% (11/17) of Grade III oligodendrogliomas as compared to 35% (6/17) in Grade II oligodendrogliomas.
3) The biological significance of these findings will be better understood with studies on a larger cohort of patients and clinical follow-up.
Category: Neuropathology

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 246, Wednesday Afternoon

 

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