Grade II oligodendrogliomas can be treated without radiation therapy in a few cases after surgery, and most patients do require radiation therapy. Gliomas are usually classified into one to four grades; grade one is considered benign and can be treated without radiotherapy after surgery, while grade three to four are malignant tumors that require radiotherapy after surgery. Grade II oligodendrogliomas are considered to be malignant tumors, and if they can be completely removed during surgery, postoperative radiotherapy may be considered as a temporary measure, with further observation and regular review of the cranial magnetic resonance imaging (MRI). Usually, grade 2 oligodendroglioma has infiltrative growth, has no clear boundary with the surrounding brain tissues or the tumor is located in the functional brain area, and it is often impossible to remove the brain tumor completely or totally during surgery. The residual tumor can recur quickly after surgery, in which case radiation therapy such as Gamma Knife or Radio Wave Knife is considered to be given routinely to avoid or delay the recurrence of the tumor. After surgery for grade II oligodendroglioma, you need to go to a regular hospital for consultation with neurosurgery and oncology to decide whether radiation therapy is needed.