[Diffuse Astrocytoma with Malignant Progression after Long-term Temozolomide Monotherapy:A Case Report]

The 2016 World Health Organization brain tumor classification update may change the clinical approach toward treatment of diffuse astrocytoma(DA). Thus, more information about such cases is required. We report a case of DA, which was previously diagnosed as oligoastrocytoma. The tumor showed malignant progression after long-term temozolomide monotherapy. A 78-year-old woman presented with forgetfulness and decreased activity 12 years ago. MRI identified a T2-hyperintense lesion in the right frontal lobe. Histological diagnosis following partial resection was oligoastrocytoma. The residual tumor shrank after 65 courses of maintenance temozolomide monotherapy, which was terminated five years ago. The remaining lesion started enlarging gradually two years ago, showing enhancement on post-contrast T1WI and hyperintensity on arterial spin labeling, indicating malignant progression. The patient underwent maximum resection. The primary and the recurrent tumors were histologically reviewed. The former comprised of oligodendroglial and astrocytic tumor cells positive for IDH1 mutations and negative for ATRX mutations. The Ki67 index was 2.6%. Using the MethylationEPIC array, we generated a copy number profile and confirmed that the 1p/19q status was intact. The patient was ultimately diagnosed with IDH-mutant DA. The recurrent tumor showed marked proliferation of atypical glial cells with microvascular proliferation and the same immunophenotype as the primary tumor, with a Ki67 index of 13.1%. Thus, it was diagnosed as an IDH-mutant anaplastic astrocytoma and was treated with postoperative radiochemotherapy. Currently, multimodal therapy selection may be performed during initial treatment. Thus, an integrated diagnostic approach based on both histological and molecular findings is essential to identify the optimal treatment.