JAK2V617F allele burden prior to and during PEG-IFN-α-2a therapy based on TET2 mutational status. Patients with JAK2V617F mutations in addition to TET2 mutations (n = 6) had a significantly higher JAK2V617F allele burden at the onset of therapy compared with their TET2 wild-type/JAK2 mutant counterparts (P = .04; Mann-Whitney U test). Moreover, patients with TET2/JAK2 comutations did not experience a significant decrement in JAK2V617F allele burden in contrast with JAK2 mutant/TET2 wild-type patients.