1p/19q co-deletion is a pathognomonic biomarker that defines a distinct glioma entity and is characteristic of oligodendrogliomas. The presence of 1p/19q co-deletion is a strong independent prognostic biomarker associated with improved survival in both diffuse low-grade and anaplastic tumours.1p/19q-co-deletion has predictive value for response to chemotherapy in anaplastic oligodendrogliomas. FISH is unable to differentiate between the whole chromosome arm deletions with centromeric breakpoints characteristic of 1p/19q co-deleted oligodendrogliomas, from smaller focal deletions. This distinction is important given the association of 1p/19q whole-arm co-deletion with improved survival and response to chemotherapy in the oligodendroglial tumour subtype.
FISH probes targeting 1p and 19q regions were used to determine deletion status of oligodendrogliomas patients having grades II or III disease. FISH was performed on 4 μm thick tissue sections using Abbott Molecular (USA) dual color probe sets [LSI 1p36/LSI 1q25 and LSI 19p13/LSI 19q13] according to the manufacturer’s instructions. A total of 60 nuclei were examined. The ratio was calculated for 1p and 19q deletion by dividing 1p or 19q signals by their respective control signals;
This study investigated 99 patients of oligodendroglioma enrolled between 2013 and 2016 at the Aga Khan University Hospital. 2016. The male to female ratio was 2:1. Mean age was 39 years and patients’ ages ranged from 13 to 79 years. Thirty-five (35%) cases demonstrated co-deletion of 1p/19q, 2 cases showed isolated 1p deletion, whereas 19q deletion was positive in 9 patients. Among patients exhibiting 1p/19q co-deletion, 17 cases (48.5%) were grade II tumors and 16 cases (45.7%) were grade III tumors. Two (5.7%) of the cases had features intermediate between grade II and III.
On the basis of our findings, patients with 1p/19q-co-deleted anaplastic oligodendroglial tumours should not be treated with radiotherapy alone, but instead receive early alkylating chemotherapy with radiotherapy. A similar approach should be considered in a subset of patients with grade II oligodendroglioma.
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All authors have declared no conflicts of interest.