Brain cancers
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Brain Cancers: Incidence, Types, and Challenges
Global Incidence and Burden of Brain Cancers
Brain and central nervous system (CNS) cancers are significant sources of morbidity and mortality worldwide. In 2016, there were approximately 330,800 new cases and 227,800 deaths globally due to CNS cancers. The age-standardized incidence rates of these cancers increased by 17.3% from 1990 to 2016, with the highest rates observed in regions with higher socio-demographic indices (SDI) such as East Asia, Western Europe, and the USA. The global burden of CNS cancers, measured in disability-adjusted life years (DALYs), remained substantial, with notable regional variations reflecting differences in diagnostic and reporting practices.
Types of Primary Brain Tumors
Gliomas and Glioblastomas
Gliomas are the most common malignant primary brain tumors in adults, with glioblastoma being the most aggressive subtype. Despite advances in molecular biology that have improved the understanding of glioma pathogenesis, the five-year survival rate for glioblastoma remains dismally low, increasing only from 4% to 7% over several decades . Molecular genetic alterations such as IDH mutations and 1p/19q codeletions are now integral to the classification and treatment planning of gliomas, as per the revised 2016 WHO classification.
Meningiomas
Meningiomas are the most common non-malignant brain tumors, accounting for 38.3% of all brain tumors. They are more prevalent in females and are often managed through surgical resection, with radiation therapy and chemotherapy reserved for high-risk or refractory cases .
CNS Lymphomas
Primary CNS lymphomas have seen a significant increase in incidence over the past two decades. Treatment typically involves methotrexate-based chemotherapy combined with radiotherapy, although this combination can be neurotoxic, particularly in elderly patients.
Epidemiological Trends and Survival Rates
In the United States, the incidence of malignant brain tumors has shown a slight decline of 0.8% annually from 2008 to 2017, while non-malignant tumors have seen higher rates in females and non-Hispanic Black individuals. The five-year relative survival rate for malignant brain tumors has improved from 23% to 36% between 1975 and 2015, with more significant gains observed in younger age groups. However, survival disparities persist, particularly among racial and ethnic minorities.
Challenges in Treatment and Research
Brain tumors remain among the most challenging cancers to treat due to their resistance to conventional and novel therapies. The unique properties of neural tissues contribute to this resistance. Current research efforts are focused on developing molecular targeted therapies, immunotherapies, gene therapies, and novel drug-delivery technologies. However, single-agent therapies have been largely disappointing, necessitating combination therapies for a more effective antitumor response .
Conclusion
Brain and CNS cancers pose a significant global health challenge with increasing incidence rates and substantial morbidity and mortality. While advances in molecular biology and genomics have improved the understanding and classification of these tumors, effective treatments remain elusive, particularly for aggressive subtypes like glioblastoma. Continued research and investment are crucial to overcoming the challenges in diagnosing and treating brain cancers, with a focus on developing combination therapies and addressing survival disparities among different populations.
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