Glioblastoma incidence is rising in several parts of the world, though the picture is more nuanced than a simple yes or no. International studies report glioblastoma occurs at a rate of 0.59 to 5 per 100,000 people, with increasing rates documented across South America, Eastern Europe, and Southern Europe. In the United States, the trend depends heavily on age: rates are climbing among younger adults while holding steady or declining in older groups.
Where Rates Are Climbing
A 2017 international analysis found increasing rates of brain cancers in countries across South America, Eastern Europe, and Southern Europe. Japan was the only country where rates were clearly declining. This broad geographic spread suggests the rise isn’t limited to a single region or healthcare system, though countries with more advanced diagnostic infrastructure tend to report higher rates overall.
In the United States, data from 1999 to 2020 shows the overall incidence of brain cancer peaked in 2019. But the trend varies dramatically by age. People under 35 saw a significant rise in incidence over that period. Meanwhile, every age group from 35 onward showed stable or declining rates. This split has puzzled researchers, since glioblastoma has traditionally been considered a disease of older adults, with the highest rates occurring in people 75 and older (about 20 cases per 100,000).
Who Gets Glioblastoma Most Often
Glioblastoma remains far more common in older adults. The crude rate per 100,000 people rises steeply with age: 3.1 in people under 15, 6.4 in the 45 to 54 range, 11.4 for ages 55 to 64, and 20.1 for those 75 and older. Men are diagnosed more often than women, at a rate of 7.5 versus 5.7 per 100,000. White patients account for nearly 89% of cases in U.S. data, with a rate of 7.4 per 100,000 compared to 3.4 for Black patients and 3.2 for Asian or Pacific Islander patients.
Better Imaging May Explain Part of the Rise
One reason incidence appears higher now is that doctors are simply better at finding tumors. Over the past three decades, MRI and CT scanning have become far more widely available. MRI with contrast dye is the standard tool for diagnosing brain tumors, while CT is typically the first scan ordered for acute neurological symptoms like sudden headaches with focal symptoms or altered consciousness. As more people receive brain scans for a wider range of complaints, tumors that might have gone undetected in earlier decades are now being caught. This detection effect makes it difficult to separate a true biological increase from an apparent one driven by better surveillance.
How the Definition of Glioblastoma Changed
The way glioblastoma is classified has shifted significantly, which complicates trend tracking. In 2021, the World Health Organization overhauled its classification of brain tumors. Previously, some tumors with a specific genetic mutation (called IDH-mutant) could still be labeled glioblastoma based on how they looked under a microscope. Under the new system, glioblastoma is strictly defined as IDH-wildtype, meaning it lacks that mutation. Tumors that would formerly have been called glioblastoma but carry the IDH mutation are now classified as a different tumor type entirely.
This reclassification means the pool of tumors counted as “glioblastoma” has narrowed. Going forward, incidence numbers may appear to shift not because the actual number of aggressive brain tumors changed, but because some cases moved into a different diagnostic category. Any comparison of glioblastoma rates before and after 2021 needs to account for this change.
Suspected Environmental Risk Factors
Researchers have investigated several environmental exposures that may contribute to glioblastoma risk, though none has been definitively established as a cause. Agricultural pesticide exposure stands out as one of the most studied occupational risks, with large cohort studies linking it to increased brain tumor rates. Radon, the naturally occurring radioactive gas that seeps into homes from the ground, is an often-overlooked factor that has been associated with higher glioma incidence in some studies. Military personnel exposed to microwave and radiofrequency radiation have shown elevated brain cancer rates. Ultrafine particles from burn pits and vehicle exhaust have also been investigated for their potential to trigger the genetic changes that lead to glioblastoma, but the evidence remains preliminary.
The Mobile Phone Question
The potential link between cell phone use and brain tumors remains one of the most debated topics in this space. A large meta-analysis combining data from 19 case-control studies and five cohort studies found mixed results. The cohort studies, which are generally considered more reliable, showed no statistically clear connection between cell phone use and glioma.
Case-control studies, however, told a more concerning story. People who used their phone on the same side of their head where the tumor developed had a 45% higher odds of glioma compared to non-regular users. Those who used phones for more than 10 years had a 32% higher odds. And users with over 896 cumulative hours of phone use had a 66% higher odds of glioma. These findings are suggestive but come with important caveats: case-control studies rely on people accurately remembering their past phone habits, and people diagnosed with brain tumors may recall their phone use differently than healthy participants. The overall scientific consensus remains uncertain rather than alarming.
Survival Remains Stubbornly Low
Despite the attention glioblastoma receives, outcomes have improved only modestly over the past two decades. Median survival after standard treatment, which involves surgery followed by radiation and chemotherapy, is approximately 12 to 15 months. Fewer than 30% of patients survive two years, and the five-year survival rate remains below 10%. This makes glioblastoma one of the most lethal cancers in adults.
One recent bright spot applies to a related but distinct tumor type. In 2024, the FDA approved vorasidenib, an oral drug for low-grade gliomas carrying IDH mutations. In clinical trials, the drug more than doubled the time before tumors progressed (27.7 months versus 11.1 months with placebo) and significantly delayed the need for radiation, chemotherapy, or additional surgery. Only 3.6% of patients had to stop taking it due to side effects. However, vorasidenib targets IDH-mutant tumors, which are no longer classified as glioblastoma under the 2021 system. For IDH-wildtype glioblastoma itself, no comparable breakthrough has emerged.
What the Projections Show
The global burden of brain cancer is expected to grow in the coming years, driven largely by aging populations. WHO projections estimate that the European Region alone will see roughly 85,000 new brain and central nervous system cancer cases and nearly 70,000 deaths by 2030, up from about 82,000 new cases and 58,000 deaths reported in 2015. These projections reflect not only any true increase in incidence but also the simple math of more people living into the age groups where brain tumors are most common. As populations age worldwide, the absolute number of glioblastoma cases will almost certainly rise even if the age-adjusted rate stays flat.