Fen Zhao,1,2,* Minghuan Li,1,2,* Li Kong,1,2 Guoli Zhang,1,2 Jinming Yu1,21Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong Academy of Medical Sciences, 2Key Laboratory of Radiation Oncology Shandong Province, Jinan, Shandong, People’s Republic of China*These authors contributed equally to this workAbstract: Glioblastoma is the most aggressive and lethal primary malignancy of the brain, and radiotherapy (RT) is a fundamental part of its treatment. However, the optimal radiation treatment conditions are still a matter of debate, and there is no clear consensus concerning the inclusion of peritumoral edema in the clinical target volume calculation. Target delineation calculations that use postoperative residual tumor and cavity volumes plus 2 cm margins result in smaller volumes of normal brain receiving high-dose irradiation, compared to calculations that include expanded edema. Smaller RT fields may be more appropriate than larger RT fields, possibly reducing the risk of late neurological deterioration, especially in patients with significant peritumoral edema. This review focuses on the factors influencing target delineation, such as peritumoral edema, failure patterns, and prognostic factors (clinical and pathological characteristics) of patients with glioblastoma. Based on this information, we make three suggestions for radiation oncologists to refer to in daily practice. Further study is necessary to investigate the unresolved problems related to routine clinical application of RT.Keywords: glioblastoma, radiotherapy, target volume, postoperative