Oligodendroglioma

Oligodendrogliomas carrying the necessary genetic features (IDH alteration and 1p/19q loss) have one of the best prognoses among brain tumors. It grows slowly and responds well to both chemotherapy and radiation therapy; therefore, many patients can live for many years. Compared to faster and more aggressive brain tumors, it has a much more favorable prognosis. Tumors without these genetic features fall into a different group (astrocytoma) and have different outcomes.

1p/19q loss is a genetic feature meaning that certain portions of two chromosomes are missing in tumor cells. According to current classification, the presence of this chromosomal loss, together with another genetic alteration called IDH, is mandatory for the diagnosis of oligodendroglioma; without these features, the diagnosis of oligodendroglioma cannot be made. This genetic feature also makes the tumor sensitive to chemotherapy and radiation therapy, meaning it responds well to treatment. The test is performed on the tumor tissue obtained.

Yes. Vorasidenib is a recently approved oral medication for Grade 2 brain tumors (IDH-mutant oligodendroglioma and astrocytoma). Studies have shown that it significantly prolongs the time patients live without disease progression. It is taken once daily and is generally well tolerated. With this medication, long-term control can be achieved in low-risk Grade 2 oligodendroglioma patients after surgery; in some cases, radiation and chemotherapy can be delayed. Which patient is suitable is determined based on tumor characteristics.

PCV (a treatment consisting of three drugs) is a long-established treatment in oligodendroglioma proven to extend survival; it is administered in specific cycles. Temozolomide is an alternative medication; it is easier to tolerate and has fewer side effects, but it has not been proven as conclusively effective as PCV. Therefore, PCV is generally preferred in young patients and those in good general condition; temozolomide may be preferred in elderly patients or those with comorbidities. The decision is made individually by the team based on the patient's condition.

In low-risk Grade 2 tumors (young age, gross total resection, small tumor), an oral medication (vorasidenib) or close observation (watchful waiting) after surgery may be sufficient. In higher-risk Grade 2 tumors (advanced age, partial tumor resection, large tumor) and all Grade 3 tumors, radiation therapy and chemotherapy (PCV or temozolomide) are given in addition to surgery. Studies have shown that adding chemotherapy in these cases significantly extends survival. Treatment decisions are made by the team based on genetic testing, age, and general condition.

Yes, the vast majority of oligodendroglioma patients present with seizures; this is the most common initial symptom and may be the only manifestation for years. The tumor's location near the brain surface predisposes to seizures. When the tumor is removed surgically, seizures are brought under control in a significant proportion of patients. When the tumor is completely resected, antiepileptic drugs can typically be reduced and discontinued over time (usually within a few years). However, in some patients, seizures may persist and long-term medication may be necessary.

Calcification is seen on imaging in the vast majority of oligodendrogliomas; this is a typical finding for the tumor, but does not establish a definitive diagnosis on its own (calcification can occur in other tumors). Calcification is an indicator that the tumor grows slowly and has been present for a long time. It is very well visualized on CT scan. Due to calcification and vascularity, the likelihood of small hemorrhage in these tumors is slightly higher than in other brain tumors. Genetic testing (IDH alteration and 1p/19q loss) is still needed for definitive diagnosis.

Yes, Grade 2 oligodendrogliomas can transform into a higher grade (Grade 3) over the years. Signs of transformation include rapid growth on MRI, new changes within the tumor, increased surrounding edema, and worsening of symptoms (increased seizure frequency, new neurological findings, increased headache). For this reason, regular MRI follow-up is of great importance. If rapid growth is detected, rebiopsy or reoperation may be necessary. The fundamental genetic characteristics of the tumor do not change, but its grade under microscopy increases.

Awake surgery is a specialized technique used for oligodendrogliomas located near brain regions controlling important functions such as speech or movement. During a portion of the surgery, the patient is awakened; speech and movement tests are performed to determine which regions control which functions. Thus, while the tumor is removed as completely as possible, critical functions such as speech and movement are preserved. This method is suitable for patients who can cooperate, have low anxiety levels, and have tumors located near these important regions. Since oligodendroglioma frequently occurs near these areas, awake surgery is commonly used and is safe.

Since oligodendroglioma has a relatively favorable course, preserving quality of life is very important; many patients live for many years. Recommendations include: regular use of anti-seizure medications for seizure control, regular follow-up (MRI at specific intervals to detect transformation early), regular and appropriate exercise, balanced nutrition, memory and attention exercises, psychological support against depression and anxiety, participation in work and social life, and fatigue management. With modern treatments, many patients can continue their daily activities, and even their work life.