Current knowledge and treatment strategies for grade II gliomas.

World Health Organization grade II gliomas (GIIGs) include diffuse astrocytoma, oligodendroglioma, and oligoastrocytoma. GIIG is a malignant brain tumor for which the treatment outcome can still be improved. Review of previous clinical trials found the following: (1) GIIG increased in size by 3-5 mm per year when observed or treated with surgery alone; (2) after pathological diagnosis, the survival rate was increased by early aggressive tumor removal at an earlier stage compared to observation alone; (3) although the prognosis after total tumor removal was significantly better than that after partial tumor removal, half of the patients relapsed within 5 years; (4) comparing postoperative early radiotherapy (RT) and non-early RT after relapse, early RT prolonged progression-free survival (PFS) but did not affect overall survival (OS); (5) local RT of 45 to 64.8 Gy did not impact PFS or OS; (6) in patients with residual tumors, RT combined with chemotherapy (procarbazine plus lomustine plus vincristine) prolonged PFS compared with RT alone but did not affect OS; and (7) poor prognostic factors included astrocytoma, non-total tumor removal, age ≥40 years, largest tumor diameter ≥4-6 cm, tumor crossing the midline, and neurological deficit. To improve treatment outcomes, surgery with functional brain mapping or intraoperative magnetic resonance imaging or chemoradiotherapy with temozolomide is important. In this review, current knowledge regarding GIIG is described and treatment strategies are explored.