The Impact of Extent of Resection on Malignant Transformation of Pure Oligodendrogliomas

Keywords: resection, surgery, oligodendroglioma, malignant transformation, outcome

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     Recent evidence suggests greater extent of resection (EOR) extends malignant progression-free survival in low-grade glioma (LGG) patients. These studies, however, rely on combined analysis of oligodendrogliomas, astrocytomas, and mixed oligostrocytomas – three histological subtypes with distinct genetic and molecular compositions.
     To assess the value of extent of resection in a homogeneous LGG patient population and delineate its impact on LGG transformation, we examined its effect on newly-diagnosed supratentorial oligodendrogliomas.
     We identified 72 consecutive, newly-diagnosed World Health Organization (WHO) grade II oligodendroglioma adult patients treated with microsurgical resection at Barrow Neurological Institute from 2003-2010.
     Clinical and radiographic data were collected retrospectively, including region-of-interest analysis to measure tumor volumes based on fluid-attenuated inversion recovery (FLAIR) imaging.
     Median preoperative and postoperative tumor volumes and EOR were 26.0 cm3 (range, 0.4-222.7 cm3), 5.69 cm3 (range, 0-157.1 cm3), and 84.5% (range, 1%-100%), respectively. Median follow-up was 40.8 mos, with 6 deaths (8.3%). Progression and malignant progression were identified in 17 (23.6%) and 10 (13.9%) cases, respectively. Greater EOR was associated with longer progression free survival (p<0.001); however, EOR did not prolong the interval to malignant progression.
     This is a retrospective study.
     Greater EOR is associated with longer progression free survival for WHO grade II oligodendroglioma patients.
     However, for this particular low-grade glioma patient population, the interval to malignant progression is not influenced by cytoreduction. This raises the possibility that the capacity for microsurgical resection to modulate malignant progression is mediated through biological mechanisms specific to non-oligodendroglioma LGG histologies.


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