The Catch Guide to Brain Cancer

Description

The brain is the locus of countless bodily functions, and many processes that define the human condition: thought, feeling, memory, emotion, sensory experience, and expression are all centered in the brain. Together with the spinal cord, it forms the central nervous system (CNS). In most parts of the body, benign growths do not invade nearby tissues, and may not even impede the function of the primary growth site; many can simply be monitored without treatment. In the central nervous system, however, even when tumors don’t spread to other organs, their internal spread can damage vital tissues or nerves, with potentially life-altering consequences. For this reason, doctors tend to focus on brain and spinal cord tumors rather than cancers exclusively.

Certain CNS tumors are much more common in children, but the median age at diagnosis is 60. The majority of brain and spinal cord tumors are diagnosed after the age of 55. In the US, women are likelier to develop CNS tumors than men,^[1] but men are likelier to develop malignant tumors.

Brain and spinal cord tumors cause different symptoms depending on where the primary growth is located. Tumors in any part of the skull can cause intracranial pressure, which may lead to:

• Nausea/vomiting
• Blurred vision 
• Headache (especially a headache which is persistent and worsens over time) 
• Seizures
• Personality/behavior changes
• Balance issues
• Drowsiness 
• Coma (this is more rare)

There are several other possible symptoms of CNS tumors. Because different tumor locations affect different portions of the brain, most individuals are likely to experience only some of the following: 

• Weakness/numbness, especially on one side of the body
• Problems speaking or understanding words
• Changes in speech rhythm
• Difficulty thinking or focusing
• Walking issues
• Difficulty with precise movements of the hands, arms, feet, or legs
• Problems swallowing
• Vision problems
• Issues synchronizing eye movement
• Balance issues
• Hearing loss
• Facial weakness, numbness, or pain
• Bladder or bowel incontinence
• Lack of coordination in the arms/legs

These symptoms can be caused by many different conditions and should be evaluated by a medical professional. 

Brain and spinal cord tumors can present as multiple subtypes, each characterized by distinct features and biological behaviors: 

• Astrocytomas (includes glioblastomas): These tumors form in astrocytes, cells which help support and repair neurons. Astrocytomas can spread throughout the brain and blend with healthy tissue, making them very difficult to remove surgically. They can become more aggressive over time, and only rarely spread outside the CNS. Low-grade astrocytomas tend to grow slowly, while high-grade astrocytomas grow quickly and spread into surrounding brain tissues. Glioblastomas are the fastest growing variety of this type of tumor. 
• Oligodendrogliomas: These rare tumors begin in the oligodendrocytes, cells which form myelin, a substance that protects the nerve cells. As with astrocytomas, their grade indicates the level of aggressiveness. They can also become more aggressive over time.
• Meningiomas: Meningiomas form in the layers of tissue that surround the brain and spinal cord (the meninges) and account for about a third of primary CNS tumors in adults. They’re about twice as common in women and the risk of developing one increases with age. Low grade meningiomas can usually be cured by surgery, but high grade meningiomas, while rarer, tend to grow quickly, may spread to other parts of the body, and may recur after treatment. 
• Gangliogliomas: These tumors contain both neurons and glial cells, and are rare in adults. They’re typically slow growing and often curable by surgery alone. 
• Ependymomas: These rare tumors typically grow in the spinal cord or ventricles (cavities in the brain or spinal cord which contain cerebrospinal fluid, or CSF). Some can be completely removed via surgery, but because they are more likely than other tumor types to spread through CSF pathways and the ependymal cells that line those pathways, they can be complicated to treat.
• Medulloblastomas: These fast-growing tumors are much more likely to occur in children than adults, and often spread via CSF pathways. A combination of surgery, radiation, and chemotherapy can successfully treat this form of cancer. 
• Schwannomas: Schwann cells insulate the nerves, and schwannomas are almost always benign. About 8% of CNS tumors are schwannomas.
• Craniopharyngiomas: These slow-growing tumors form between the brain and the pituitary gland, either of which they may press upon, potentially causing hormonal issues. They may also cause vision problems. These are more common in children, and can be difficult to completely remove without long-term effects.
• Primary central nervous system (CNS) lymphomas: Lymphomas start in white blood cells called lymphocytes. Primary CNS lymphomas are very rare, usually occurring in individuals with immune problems, including those caused by HIV infection. Recent advances in HIV and AIDS treatment have made primary CNS lymphomas less common. These can grow quickly and may be difficult to treat.

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Survival rates and incidence

Survival rates for brain cancer vary widely based on type of tumor as well on age of diagnosis. Low-grade astrocytoma has an overall survival rate of 73% for individuals aged 20-44 at time of diagnosis, while glioblastoma has a survival rate of just 6% for individuals diagnosed between the ages of 55 and 64. The following chart, based on information from the Central Brain Tumor Registry of the United States, shows 5-year survival rates by age for several types of brain cancers:^[2]

Survival rates for some age groups and some types of brain cancer aren’t readily available, as data on rarer forms of cancer can be sparse. 

Below is the overall incidence of brain cancer by age group:

Risk Factors

There are several confirmed risk factors that contribute to an individual’s risk for brain cancer:  

• Childhood CT scan: The radiation in a CT scan, particularly one received during childhood, has been shown to increase the risk of subsequently developing brain cancer. This risk has been shown when scans were performed on the head and neck specifically,^[3] but also when scans were of distant portions of the body.^[4] 
• Radiation exposure: Radiation can damage cells and lead to changes in DNA that develop into cancer over time. For brain cancer, this risk is usually tied to radiation given to the head to treat prior cancers or other conditions.
• Processed and red meat consumption: Diets high in red and processed meats have been tied to higher rates of brain cancer, though more studies are needed to definitively confirm causation. In general, diets lower in salt, processed meat, and red meat are correlated to lower risk for multiple types of cancer. 
• Health conditions: some text
  • Severe or penetrating brain injury: Both severe and penetrating traumatic brain injuries (TBI) have been shown to increase the risk of subsequent brain cancer.^[5] Risk increases directly with increased injury severity.
  • Weakened immune system: A weakened immune system–whether congenital, linked to treatment for other cancers, due to diseases such as AIDS, or during use of anti-rejection medication for transplanted organs–can increase the risk of primary CNS lymphomas. 
  • Genetic conditions: A small percentage of brain cancers are linked to a hereditary cancer syndrome. These syndromes include: some text
    • Neurofibromatosis type 1 (or von Recklinghausen disease)
    • Neurofibromatosis type 2
    • Tuberous sclerosis
    • Von Hippel-Lindau syndrome
    • Li Fraumeni syndrome 
    • Turcot syndrome
    • Gorlin syndrome
    • Cowden syndrome

Protective Factors

Several factors have been shown to have protective effects against brain cancer:

• Maintaining a healthy weight: Numerous studies have linked higher BMI to increased risk of various types of cancer, including brain cancer. Excess body fat can lead to higher levels of estrogen and insulin, as well as increased production of insulin-like growth factors. Higher BMI is also associated with chronic low-level inflammation, which can cause DNA damage over time and contribute to the development of cancer. Maintaining a healthy weight helps you to avoid these risks. 
• Allergies / asthma / eczema: Allergies–particularly respiratory allergies such as hay fever–asthma, and eczema have all consistently been shown to decrease an individual’s risk for common types of brain cancer. The mechanisms behind this are not clearly understood, but decades of studies confirm the link.^[6] 
• Aspirin regimen: Several studies have shown an association between daily aspirin use and a reduced risk for several types of cancer, including brain. The exact mechanisms by which aspirin may reduce cancer risk are not fully understood but may involve its anti-inflammatory and antiplatelet effects. Aspirin inhibits the production of prostaglandins, which are involved in inflammation and tumor growth, and it also reduces the aggregation of platelets, which may play a role in the spread of cancer. While daily aspirin use may reduce cancer risk, it is not without potential risks of its own. Aspirin can increase the risk of gastrointestinal bleeding and other bleeding-related complications, particularly in older adults or those with a history of gastrointestinal ulcers or bleeding disorders. 
• Coffee or tea consumption: Coffee and tea consumption has been shown to lower risk of brain cancers in multiple studies.^[7] The more of either beverage one consumes, the lower the risk. 
• Oily fish consumption: Oily fish (such as salmon, mackerel, trout, sardines, and herring) are known to have various health benefits. Rich in omega-3 fatty acids, protein, vitamins, and minerals, studies have shown that eating oily fish has protective effects against several types of cancer, including brain. Increased consumption increases these benefits.
• Statins: Statins are a class of prescription drugs that lower cholesterol and can reduce the risk of heart attack and stroke, and studies have shown that statins may also lower the risk of several cancers, including brain. While the exact mechanism is unknown, this could be due to several factors. Statins have anti-inflammatory properties that may inhibit the inflammatory processes involved in cancer development and progression.
• Vegetable consumption: Vegetables are rich in various nutrients which have been shown to have protective effects against multiple cancers, including brain. These foods contain a variety of antioxidants, which help neutralize free radicals in the body and reduce inflammation.

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Screening

Early detection of brain cancer has a dramatic impact on prognosis. For all cancers, survival rates decrease the further the cancer has spread throughout the body. 

Depending on your age and risk factors, the optimal brain cancer screening will vary:

• Regular physical exams: During regular medical exams, your doctor will check your reflexes, balance, vision, muscle strength, eye and mouth movement, coordination, and alertness. Changes or abnormal results in any of these assessments may lead to a referral to a neurologist for further testing. 
• Lumbar puncture: Lumbar punctures can look for cancer cells in the cerebrospinal fluid, which can help determine location and spread of any tumors. These are not usually recommended as a way to discover tumors, as MRI imaging is safer and provides more detailed information. 

Imaging tests: MRIs show the most detailed images of the soft tissues in the CNS, and are considered the best way to look for possible tumors. CT scans can be useful in some cases, but are not usually recommended. It’s also important to note that CT scans expose the brain to radiation, while MRI scans don’t.