Epidemiology of Glioblastoma and Trends in Glioblastoma Survivorship

Incidence of glioblastoma

Gliomas are the most common type of malignant brain tumor in adults. Of the gliomas, glioblastoma (astrocytoma grade IV) is the most common, and represents approximately 27% of all primary brain tumors, and 80% of malignant primary brain tumors in the United States. Incidence of glioblastoma in the United States varies significantly by sex, race, ethnicity, and age ( Fig. 2.1 ). From 2006 to 2012, glioblastoma occurred at an overall average annual age-adjusted incidence rate (AAAIR) of 3.20 (95% confidence interval [95% CI], 3.17–3.22) per 100,000 population. Glioblastoma is 1.6 times more common in men than in women, with an AAAIR of 3.99 (95% CI, 3.94–4.03) per 100,000 in men, and 2.53 (95% CI, 2.50–2.56) per 100,000 in women. Incidence of glioblastoma is significantly higher in non-Hispanic people (AAAIR, 3.28, 95% CI, 3.25–3.31) compared with Hispanic people (AAAIR, 2.41; 95% CI, 2.33–2.50). Glioblastoma is most common in white people (AAAIR, 3.45; 95% CI, 3.42–3.48), compared with black people (AAAIR, 1.76; 95% CI, 1.69–1.82), American Indian/Alaska natives (AIAN) (AAAIR, 1.47; 95% CI, 1.25–1.70), and Asian/Pacific Islanders (API) (AAAIR, 1.60; 95% CI, 1.51–1.70). Incidence of glioblastoma increases with increasing age. Incidence is lowest among people 0 to 19 years old (AAAIR, 0.15; 95% CI, 0.13–0.16) and highest among those 75 years and older (AAAIR, 13.66; 95% CI, 13.42–13.91).

Fig. 2.1, Average annual age-adjusted incidence rates of glioblastoma by ( A ) sex, ( B ) Hispanic ethnicity, ( C ) race, and ( D ) age groups for diagnoses between 2008 and 2012. AIAN, American Indian/Alaska Native; API, Asian Pacific Islander.

Incidence time trends

There was no significant increase in incidence of glioblastoma in the United States between 2000 and 2010. This trend is similar to patterns of incidence in other countries, including Australia and the United Kingdom. Previous analyses showed an increasing incidence of malignant brain tumors during the 1980s and the 1990s, but this is thought to be the result of screening bias caused by increasing access to and use of medical imaging technologies such as computed tomography (CT) and MRI.

Survival after diagnosis with glioblastoma

Glioblastoma has one of the poorest survival rates of any malignant brain tumor, and contributes disproportionately to cancer mortality and morbidity. Median survival after diagnosis with glioblastoma is approximately 12 months, and this survival period increases to approximately 14 months when patients are treated with current standard therapy, which consists of maximal safe surgical resection followed by concurrent radiation and temozolomide. Between 2000 and 2012 in the United States, glioblastoma had a 1-year relative survival rate of 37.8% (95% CI, 37.3%–38.4%), with 5.1% (95% CI, 4.8%–5.7%) of persons surviving 5 years after diagnosis ( Fig. 2.2 ). One-year survival rates have improved since 2000, likely because of the current standard therapy being widely adopted. Survival rates over time vary significantly by age at diagnosis, with persons aged 20 to 34 years having the best overall survival. There are some small differences in 1-year survival by sex and ethnicity, but there are no significant differences by sex, ethnicity, and race in long-term survival with glioblastoma.

Fig. 2.2, One-year, 2-year, 3-year, 4-year, 5-year, and 10-year relative survival rates after diagnosis with glioblastoma by ( A ) sex, ( B ) Hispanic ethnicity, ( C ) race, and ( D ) age groups for diagnoses between 2000 and 2012.

Survival time trends

There have been significant increases in both 1-year and 5-year survival after diagnosis with glioblastoma since 1973 ( Fig. 2.3 ). From 1997 to 2012, 1-year survival increased with an annual percentage change (APC) of 3.7% (95% CI, 3.1%–4.3%) from 24.3% (95% CI, 21.4%–27.2%) at the beginning of the time period, to 43.0% (95% CI, 37.6%–48.3%) at the end of the time period. Five-year survival also increased from 1997 to 2012, with an APC of 8.0% (95% CI, 5.1%–11.0%) from 2.1% (95% 1.3%–3.3%) at the beginning of the time period to 5.6% (95% CI, 4.7%–6.7%) at the end of the time period. This trend may be caused by a wide variety of factors including increased screening and earlier detection caused by improvements in medical imaging technologies, as well as the introduction of new treatment modalities, such as the current standard therapy in the early to mid-2000s.

Fig. 2.3, Relative 1-year and 5-year overall survival after diagnosis with glioblastoma.

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