Glioblastoma
The most common length of survival following diagnosis is 12 to 15 months, with fewer than 3% to 5% of people surviving longer than five years. Without treatment survival is typically 3 months.
Oligodendroglioma
Long-term survival is reported in a minority of patients. With aggressive treatment and close monitoring, it is possible to outlive the typical life expectancies for both low grade and high grade oligodendrogliomas. Westergaard's
study (1997) showed that patients younger than 20 years had a median survival of 17.5 years. Another study shows a 34% survival rate after 20 years. However, as discussed above, such figures can be misleading since they do not factor in the types of treatment nor the genetic signature of the tumors. Additionally, such historic data loses significance due to the relatively long survival of patients (compared to other types of brain tumors) and the introduction of newer treatment options over time.