Incidence of Malignant Brain and Spinal Tumors Varies Substantially by World Region
Key findings
- Understanding the global burden of brain and spinal tumors is a critical prerequisite to addressing global health disparities
- Based on this analysis of 270 cancer registries in 70 countries, the age-standardized incidence of malignant brain tumors varied by region, from 6.76 cases per 100,000 person-years in Europe to 2.81 in Africa
- Malignant spinal tumors varied similarly, but were much more infrequent, with an estimated worldwide rate of 0.098 cases per 100,000 person-years
- The incidence of brain and spinal tumors also varied significantly between countries in different World Bank income groups, with a higher incidence in high-income countries
- Still, in countries with low, lower-middle or upper-middle incomes, the total volume of benign and malignant brain and spinal tumors was over 940,000 cases per year
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In the developing world, recent studies have identified a large unmet need for surgical services, particularly neurosurgical care. A critical prerequisite for building that capacity is to understand global disease burden. There have been comprehensive efforts to quantify central nervous system (CNS) tumors by country and socioeconomic group for a given year, but this research has not differentiated between tumor types.
Robert M. Koffie, MD, PhD, neurosurgery resident, and Brian V. Nahed, MD, MSc, associate director of the Neurosurgery Residency Program at Massachusetts General Hospital and neurosurgical oncologist at the Mass General Cancer Center, and colleagues have now estimated the incidence of brain and spinal tumors across seven regions of the world. In the Journal of Clinical Neuroscience, they describe the striking variance in the incidence of detected tumors by region and a country's income level.
Data Sources
The researchers obtained data from Cancer Incidence in Five Continents, Volume X, which is published by the International Agency for Research on Cancer and covers the years 2003 to 2007. To avoid counting individual cases multiple times, they selected 270 registries in 70 countries.
The researchers recorded 239,608 malignant brain tumors and 5,939 malignant spinal tumors. Age-standardized incidence rates (ASRs) were truncated to include only individuals ≥15 years of age. The worldwide ASR for malignant brain tumors was calculated as 4.25 cases per 100,000 person-years and for malignant spinal tumors, 0.098 per 100,000 person-years.
The source dataset does not report benign CNS tumors, brain and spinal metastases of non-CNS primary cancer or CNS lymphoma, which together constitute a majority of intracranial and spinal neoplasms. Therefore, the ASRs obtained should be considered lower bounds.
Tumor Incidence by Region
The ASRs varied substantially across regions of the world as defined by the World Health Organization:
- Europe — 6.76 cases per 100,000 person-years for malignant brain tumors and 0.165 for malignant spinal tumors
- North America — 6.48 and 0.201
- Latin America — 5.25 and 0.085
- Western Pacific — 4.16 and 0.150
- Eastern Mediterranean — 3.62 and 0.107
- Southeast Asia — 3.27 and 0.022
- Africa — 2.81 and 0.044
Tumor Incidence by Income Group
To study variation in tumor incidence according to economic development, registry data for each country were regrouped by World Bank income groups:
- High: ASR of 6.29 for malignant brain tumors and 0.181 for malignant spinal tumors
- Low, lower-middle or upper-middle: 4.81 and 0.106
Estimates of Benign Tumors
Benign tumors presumably represent a significant fraction of the global neurosurgical burden of CNS disease, so the researchers wanted to estimate their incidence even though no data were available in the source registries. Using the Central Brain Tumor Registry of the United States, they calculated the ASR ratio of benign to malignant tumors, then multiplied that factor (2.1) by the regional estimates of malignant tumor incidence.
The resulting ASRs for benign CNS tumors were:
- World — 9.19
- Europe — 14.63
- North America — 14.12
- Latin America — 11.28
- Western Pacific — 9.10
- Eastern Mediterranean — 7.89
- Southeast Asia — 6.97
- Africa — 6.04
- High-income countries — 13.69
- Non–high-income countries — 10.40
Global Burden of CNS Tumors
By multiplying the estimated incidences of malignant brain, malignant spinal and benign tumors by the regional populations, the researchers derived estimates of the number of people affected by these diseases. The totals were 239,342 per year in high-income countries and 943,516 in other countries. The worldwide annual total, calculated from the sum of World Health Organization regions, was 964,272.
These data underscore the magnitude of the need for neurosurgical services in underserved regions. Differences between regions in case ascertainment rates presumably explain a large part of the variance in tumor incidence, so the study also demonstrates the need to improve the diagnostic and reporting resources in the developing world.
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