To show superiority of an initial temozolomid plus lomustine (CETEG) chemotherapy followed by partial brain radiotherapy (RT) plus PCV (RT-PCV) at progression over partial brain radiotherapy (RT) followed by procarbazine, lomustine and vincristine (PCV) chemotherapy (RT-PCV) and best investigators choice (BIC) at progression for qualified overall survival (qOS) as defined in Section 8.3

Evaluation and comparison of the two groups regarding secondary endpoints (short-term qOS, PFS, OS, complete and partial response rate).

Newly diagnosed grade II and III gliomas (brain tumors) with 1p/19q co-deletion

1. Histologically confirmed, newly diagnosed WHO grade II or III glioma. 2. Tumor carries an isocitrate dehydrogenase (IDH) mutation (determined by immunohistochemistry (IHC) and/or deoxyribonucleic acid (DNA) sequencing). 3. Tumor is co-deleted for 1p/19q (determined by copy number variations, fluorescence in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA) or other appropriate methods). 4. Open biopsy or resection. 5. Age: 18 years. 6. Karnofsky Permormance Index (KPI) ≥60%. 7. Life expectancy > 6 months. 8. Availability of formalin-fixed paraffin-embedded (FFPE) or fresh-frozen tissue and ethylenediamine tetraacetic acid (EDTA) blood for biomarker research. 9. Standard magnetic resonance imaging (MRI) ≤ 72 post-surgery according to the present national and international guidelines. 10. Craniotomy or intracranial biopsy site must be adequately healed. 11. ≥ 2 weeks and ≤ 3 months from surgery without any interim radio- or chemotherapy or experimental intervention. 12. Willing and able to comply with regular neurocognitive and health-related quality of life tests/questionnaires. 13. Indication for postsurgical cytostatic/-toxic therapy. 14. Written Informed consent. 15. Female patients with reproductive potential have a negative pregnancy test (serum or urine) within 6 days prior to start of therapy. Female patients are surgically sterile or agree to use adequate contraception during the period of therapy and 6 months after the end of study treatment, or women have been postmenopausal for at least 2 years.1 16. Male patients are willing to use contraception

1. Participation in other ongoing interventional clinical trials. 2. Insufficient tumor material for molecular diagnostics. 3. Inability to undergo MRI. 4. Abnormal (≥ Grade 2 CTCAE v5.0) laboratory values for hematology (Hb, WBC, neutrophils, or platelets), liver (serum bilirubin, ALT, or AST) or renal function (serum creatinine). 5. Active tuberculosis; known HIV infection or active Hepatitis B (HBV) or Hepatitis C (HCV infection, or active infections requiring oral or intravenous antibiotics or that can cause a severe disease and pose a severe danger to lab personnel working on patients' blood or tissue (e.g. rabies).Any prior anti-cancer therapy or co-administration of anti-cancer therapies other than those administered/allowed in this study. History of low-grade glioma that did not require prior treatment with chemotherapy or radiotherapy is not an exclusion criterion. 7. Immunosuppression not related to prior treatment for malignancy. 8. History of other malignancies (except for adequately treated basal or squamous cell carcinoma or carcinoma in situ) within the last 5 years unless the patient has been disease-free for 5 years. 9. Any clinically significant concomitant disease (including hereditary fructose intolerance) or condition that could interfere with, or for which the treatment might interfere with, the conduct of the study or the absorption of oral medications or that would, in the opinion of the Principal Investigator, pose an unacceptable risk to the patient in this study. 10. Any psychological, familial, sociological, or geographical condition potentially hampering compliance with the study protocol requirements and/or follow-up procedures; those conditions should be discussed with the patient before trial entry. 11. Pregnancy or breastfeeding. 12. History of hypersensitivity to the investigational medicinal product or to any drug with similar chemical structure or to any excipient present in the pharmaceutical form of the investigational medicinal product. 13. QTc time prolongation > 500 ms. 14. Patients under restricted medication for procarbazine, lomustine, vincristine and temozolomide (see list of restricted medication in Appendix 1). 15. Liver disease characterized by: o ALT or AST (≥ Grade 2 CTCAE v5.0) confirmed on two consecutive measurements OR o Impaired excretory function (e.g., hyperbilirubinemia) or synthetic function or other conditions of decompensated liver disease such as coagulopathy, hepatic encephalopathy, hypoalbuminemia, ascites, and bleeding from esophageal varices (≥ Grade 2 CTCAE v5.0) OR o Acute viral or active autoimmune, alcoholic, or other types of acute hepatitis 16. Known uncorrected coagulopathy, platelet disorder, or history of non-drug induced thrombocytopenia. 17. History of autoimmune disease, including but not limited to myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis; autoimmune-related hypothyroidism (patients on a stable dose of thyroid replacement hormone are eligible for this study) and type I diabetes mellitus (patients on a stable dose of insulin regimen are eligible for this study). 18. Vaccination with life vaccines during treatment and 4 weeks before start of treatment. 19. Existing neuromuscular diseases, especially neural muscular atrophy with segmental demyelination (demyelising form of Charcot-Marie-Tooth syndrome) 20. Chronic constipation and subileus 21. Combination treatment with mitomycin (risk of a pronounced bronchospasm and acute shortness of breath) 22. Hypersensitivity to dacarbazin (DTIC)