Table 8. Adjuvant treatment for patients with WHO grade 2 diffuse astrocytoma (IDH-mutant) and oligodendroglioma (IDH-mutant, 1p/19q codeletion) by KSNO, NCCN, and EANO guideline.

Guidelines	Adjuvant treatment
KSNO	- High risk group*
		1) Standard RT & neoadjuvant or adjuvant PCV chemotherapy
		2) Standard RT with concurrent and adjuvant temozolomide chemotherapy
		3) Standard RT with adjuvant temozolomide chemotherapy
	- Low risk group†
		1) Observation
		2) Standard RT alone
		3) Adjuvant PCV chemotherapy alone
NCCN	- High risk group*
		1) Standard RT with adjuvant PCV chemotherapy
		2) Standard RT with adjuvant temozolomide chemotherapy
		3) Standard RT with concurrent and adjuvant Temozolomide chemotherapy
	- Low risk group†
		1) Consider clinical trial
		2) Observation
EANO	- Diffuse astrocytoma
		1) Wait-and-see or
		2) RT (50–54 Gy in 1.8–2.0 Gy fractions) followed by PCV (or temozolomide CCRT)
	- Oligodendroglioma, IDH-mutant, 1p19q codeleted and Oligodendroglioma, NOS
		1) Wait- and- see
		2) RT (50–54 Gy in 1.8–2.0 Gy fractions) followed by PCV chemotherapy

^*High risk includes patients who are older than 40 years or those who have not undergone gross total resection of the tumor; ^†Low risk includes patients who are younger than 40 years and those who have undergone gross total resection of the tumor. CCRT, concurrent chemoradiotherapy; EANO, European Association of Neuro-Oncology; IDH, isocitrate dehydrogenase; KPS, Karnofsky Performance Scale; KSNO, Korean Society for Neuro-Oncology; MGMT, O⁶-methylguanine-DNA-methyltrasferase; NCCN, National Comprehensive Cancer Network; PCV, procarbazine, CCNU, and vincristine; RT, radiotherapy; WHO, World Health Organization