Loss of heterozygosity (LOH) at 1p19q due to derivative chromosome loss from an unbalanced translocation t(1:19)(q10:p10) is reported to occur with a frequency of ~40% in patients with oligoastrocytoma and 60-80% in oligodendrogliomas. Interestingly, 1p/19q co-deletion is only found in patients with a concomitant alteration in IDH1. Additionally, these patients have been shown to have better prognosis than those having only IDH1 mutated. While this supports the prognostic value of 1p/19q co-deletion, this alteration has also been found to have predictive value in gliomas. Carriers have increased survival compared to non-carriers as well as increased sensitivity to a specific chemotherapeutic regimen (procarbazine, lomustine, and vincristine) (Annals of Translational Medicine (2015) 3(7): 95).