A new study found that incidence rates for malignant brain tumors and other central nervous system (CNS) tumors in the United States fell 0.8% per year from 2008 to 2017 for all ages combined. The decline was driven by trends in adults, while rates in children and adolescents increased slightly by 0.5% to 0.7% per year over the same period. The report, appearing in CA: A Cancer Journal for Clinicians, evaluated contemporary patterns in brain tumor occurrence in the context of incidence, mortality and survival trends in the US.
This joint study with researchers from the United States Central Brain Tumor Registry, led by Kimberly D. Miller, MPH, American Cancer Society, also found that while malignant brain tumors and other CNS tumors are rare in the U.S., they are responsible for a significant burden of cancer mortality due to their high mortality rate. By 2021, it is estimated that 83,570 people will be diagnosed with brain and other CNS tumors in the US (24,530 malignant tumors and 59,040 non-malignant tumors), and 18,000 people will die from the disease.
While incidence rates for malignant tumors are declining overall, survival remains low – only 36% of patients survive more than 5 years after diagnosis, compared to 26% for patients diagnosed in the mid-1970s. The slow progress largely reflects a lack of progress in the early detection and treatment of glioblastoma, for which the 5-year survival rate only increased from 4% to 7% over this period. Glioblastoma is responsible for 49% of all malignant brain cancers in the US
The incidence rates for non-cancerous tumors, which disproportionately affect women and black people, are slowly increasing, probably due to improvements in case finding and greater awareness. For example, the incidence of meningioma, which accounts for 54% of all non-cancerous cases in the US, increased by 0.9% per year among adults from 2008 to 2017. While 5-year relative survival for all non-malignant tumors remains high (92%), patients often experience debilitating long-term effects of their tumor and/or its treatment.
The report also found lingering differences between children. For example, death rates are the same in white and black children, despite a lower incidence in black children, reflecting a lower 5-year survival rate (70% vs. 79%), respectively. The largest black-and-white differences for children diagnosed between 2009 and 2015 were for diffuse astrocytomas (75% vs 86%, respectively) and embryonic tumors (59% vs 67%).
“While the molecular understanding of how brain cancers differ from one another is rapidly advancing, we still know little about why these tumors develop in the first place. To facilitate a better understanding, it is critical to have access to timely , comprehensive data on occurrence,” said Molenaar. “This is especially important to understand the causes of gender, age and racial/ethnic differences, especially for rarer subtypes and among understudied populations.”
The report also noted differences in incidence by gender:
The incidence of malignant brain tumors was higher in males (8.3 cases per 100,000) compared to females (6.0). Conversely, incidence rates for non-malignant tumors were higher in women (20.3) compared to men (12.8). For malignant tumors, the sex differences were greatest among those aged 45 years or older, among which the rates in women were 30% lower than in men. For non-malignant tumors, sex differences peaked between the ages of 25-29, including rates in women >2 times that in men (10.2 vs. 4.7 per 100,000), a pattern driven by high pituitary adenoma rates in women in this age group.
Materials supplied by American Cancer Society. Note: Content is editable for style and length.