biopsy for people with malignant glioma (high-grade) is unknown. for high-grade gliomas, a 2003 meta-analysis compared radiotherapy with radiotherapy and chemotherapy. it showed a small but clear improvement from using chemotherapy with radiotherapy. a 2019 meta-analysis suggested that for people with less aggressive gliomas, radiotherapy may increase the risk of long term neurocognitive side effects. whilst, evidence is uncertain on whether there are long term neurocognitive side effects associated with chemoradiotherapy. temozolomide is effective for treating glioblastoma multiforme (gbm) compared to radiotherapy alone. a 2013 meta-analysis showed that temozolomide prolongs survival and delays progression, but is associated with an increase in side effects such as blood complications, fatigue, and infection. for people with recurrent gbm, when comparing temozolomide with chemotherapy, there may be an improvement in the time-to-progression and the person's quality of life, but no improvement in overall survival, with temozolomide treatment. evidence suggests that for people with recurrent high-grade gliomas who have not had chemotherapy before, there are similar survival and time-to-progression outcomes between treatment with temozolomide or the chemotherapy multidrug known as pcv (procarvazine, lomustine and vincristine). a mutational analysis of 23 initial low-grade gliomas and recurrent tumors from the same patients has challenged the benefits and usage of temozolomide. the study showed that when lower-grade brain tumors of patients are removed and patients are further treated with temozolomide, 6 out of 10 times the recurrent tumors were more aggressive and acquired alternative and more mutations. as one of the last authors, costello, stated "they had a 20- to 50-fold increase in the number of mutations. a patient who received surgery alone who might have had 50 mutations in the initial tumor and 60 in the recurrence. but patients who received tmz might have 2,000 mutations in the recurrence." further, new mutations were verified to carry known signatures of temozolomide induced mutations. the research suggests that temozolomide for the treatment of certain brain tumors should be thoroughly thought. unjudicious usage of temozolomide might lower the prognosis of the patients further, or increase their burden. further understanding of the mechanisms of temozolomide induced mutations and novel combination approaches could be promising. prognosis prognosis of gliomas is given in relation to what grade (as scored by the world health organization system) of tumour the patient presents with. typically, any tumour presenting as above who grade i (i.e. a malignant tumour as opposed to a benign tumour) will have a prognosis resulting in eventual death, varying from years (who grade ii/iii) to months (who grade iv). prognosis can also be given based on cellular subtype, which may also impact prognosis. low grade for low-grade tumors, the prognosis is somewhat more optimistic. patients diagnosed with a low-grade glioma are 17 times as likely to die as matched patients in the general population. the age-standardized 10-year relative survival rate was 47%. one study reported that low-grade oligodendroglioma patients have a median survival of 11.6 years; another reported a median survival of 16.7 years. unfortunately, approximately 70% of low-grade (who grade-ii) will progress to high-grade tumours within 5–10 years grade ii gliomas, despite often being labeled as benign, are considered a uniformly fatal illness. high grade this group comprises anaplastic astrocytomas and glioblastoma multiforme. whereas the median overall survival of anaplastic (who grade iii) gliomas is approximately 3 years, glioblastoma multiforme has a poor median overall survival of c. 15 months. postoperative conventional daily radiotherapy improves survival for adults with good functional well‐being and high grade glioma compared to no postoperative radiotherapy. hypofractionated radiation therapy has similar efficacy for survival as compared to conventional radiotherapy, particularly for individuals aged 60 and older with glioblastoma. diffuse midline glioma main article: diffuse intrinsic pontine glioma diffuse midline glioma (dmg), previously known as diffuse intrinsic pontine glioma (dipg), primarily affects children, usually between the ages of 5 and 7. the median survival time with dipg is under 12 months. surgery to attempt tumour removal is usually not possible or advisable for pontine gliomas. by their very nature, these tumours invade diffusely throughout the brain stem, growing between normal nerve cells. aggressive surgery would cause severe damage to neural structures vital for arm and leg movement, eye movement, swallowing, breathing, and even consciousness. trials of drug candidates have been unsuccessful. the disease is primarily treated with radiation therapy alone. idh1 and idh2-mutated glioma patients with glioma carrying mutations in either idh1 or idh2 have a relatively favorable survival, compared with patients with glioma with wild-type idh1/2 genes. in who grade iii glioma, idh1/2-mutated glioma have a median prognosis of ~3.5 years, whereas idh1/2 wild-type glioma perform poor with a median overall survival of c. 1.5 years. in glioblastoma, the difference is larger. there, idh1/2 wild-type glioblastoma have a median overall survival of 1 year, whereas idh1/2-mutated glioblastoma have a median overall survival of more than 3 years.