Astrocytoma is the most common type of primary brain tumor. These tumors arise from support cells in the brain known as astrocytes, or glial cells. Astrocytomas are also referred to as gliomas.
Astrocytomas can be divided into four grades:
Grade I Astrocytomas are benign, and can be cured with surgical resection. Grade I astrocytomas include Pilocytic Astrocytomas.
Grade II Astrocytomas are considered low grade. They can be successfully managed long-term but require close monitoring, as they can transform into high grade tumors.
Grade III (Anaplastic) and Grade IV (Glioblastoma Multiforme) tumors are considered cancerous. They are aggressive and require expeditious treatment.
There are a wide range of effective surgical and non-surgical therapies now available for the treatment of astrocytomas.
Symptoms of astrocytoma can be nonspecific, and often overlap with a variety of other minor and serious brain conditions. Symptoms vary depending on the location of the astrocytoma and can include:
- Headaches, especially in the morning and progressively worsening headaches
- Personality changes
- Altered mental status
- Nausea and vomiting
- Vision changes
- Speech difficulties
- Loss of balance and gait instability (ataxia)
These symptoms could be indicators of other medical conditions such as migraine, stroke, Alzheimer’s, or trauma. Evaluation by a specialist is required to make a proper diagnosis.
Causes & Risk Factors
In general, tumors grow from normal cells in the body that have sustained damage to their DNA. Once damage occurs, these cells no longer grow and divide in a regulated, orderly fashion. The resulting mass of cells can crowd out or push against nearby organs and structures (benign tumors). For a benign tumor to become cancerous (malignant), additional DNA damage must occur that allows these cells to invade adjacent structures, or travel to distant sites in the body (metastasize).
Several risk factors are associated with benign and cancerous tumor growth:
- Age: Aggressively growing brain tumors are more common in adults over 35 years old, while slow-growing astrocytomas are more common in children and young adults.
- Radiation exposure: Ionizing radiation exposure is a significant factor for development of the brain tumor. Ionizing radiation includes XRays, radiation treatments for cancers, and nuclear waste/contamination. There is no evidence that electromagnetic radiation from electrical power lines, microwaves, or cell phones cause brain cancer.
- Family history/genetic factors: History of familial brain cancer, e.g. glioma, could be a risk factor in a small number of cases. Among other genetic conditions, Neurofibromatosis Type 1 was associated with slightly higher incidences of low-grade astrocytomas, e.g. pilocytic. Subependymal giant cell astrocytomas were associated with a genetic condition called tuberous sclerosis.
Because symptoms of a brain tumor can be vague and nonspecific, a detailed history needs to be taken regarding the nature and duration of symptoms, factors that make symptoms better or worse, and associated factors such as weakness, numbness, or seizures. This will be followed by a comprehensive neurological exam that looks for deficits, if present, that may be subtle.
The preferred imaging for astrocytoma is MRI, as this test provides the greatest detail of brain structures. If an MRI cannot be performed, CAT (computer tomography) scan with contrast or PET (position emission tomography) scan can be performed instead.
Many tumors have a characteristic appearance on MRI or CAT scan. However, in order to develop an exact treatment plan, a firm diagnosis must be made. Often, this is accomplished via stereotaxic biopsy, a surgical procedure that uses computer navigation to place a biopsy needle within the tumor in order to obtain core samples for analysis.
Tissue collected during biopsy is sent to the laboratory for evaluation under a microscope by the pathologist. Microscopic analysis will show whether the tumor is benign (non-cancerous) or malignant (cancerous), what type of cells it derives from, and the grade of tumor. This information will allow your team to formulate a treatment plan.
Treatment of astrocytoma depends on the location, size, grade of the tumor, your age, overall health, and past medical history.
Initial treatment may include a prescription of steroid medications to reduce swelling around the tumor, and to decrease pressure on nearby structures. Anti-seizure medications might also be prescribed.
Low grade tumors (confirmed by biopsy) are often observed with serial imaging, especially if they are in delicate locations, and are not causing any immediate problems.
For more easily-accessible tumors, the preferred treatment is maximal safe surgical resection. Computer modeling is used in the operating room to help plan surgical trajectories, and minimize irritation to important structures nearby. Other tools routinely used to maximize safety include lasers, intraoperative MRI, and even awake surgery.
If part of the astrocytoma invades an important location of the brain, it may not be possible to safely remove that part of the tumor. In that case, some tumor material is left behind rather than risk brain damage. The smaller volume of remaining tumor can then be treated in other ways.
Additional treatment modalities commonly used in combination with surgical resection are radiation therapy and chemotherapy.
Radiation Therapy (RT)
Radiation therapy usually follows resection of the tumor, but sometimes could be used to shrink the tumor before the surgery. Radiation therapy is provided by the radiation oncology doctor with the use of a special machine that directs a beam of high-energy particles (X-Rays or protons) to the location of tumor to kill remaining cells and/or shrink the tumor.
Types of radiation therapy include:
- Image-guiding radiation therapy and Intensity-Modulated Radiation Therapy techniques use 3D brain CT images, CT scans or X rays taken before or during the treatment session to deliver beams of radiation of different intensities and angles to the tumor location.
- Proton therapy, or proton beam therapy, is used for tumors located near sensitive. Protons release most of their energy within the tumor, leaving surrounding tissue relatively undamaged.
The machines that are used for delivering RT have different names, such as GammaKnife, CyberKnife, and LinAc (Linear Accelerator).
Radiation therapy can produce some side effects as well, such as: nausea, headaches, tiredness, loss of appetite, red, sore, inflamed skin and other effects, that are more specific to brain tumor location.
Chemotherapy is another adjuvant treatment for astrocytomas, that is commonly used together with radiation therapy to achieve better results. Chemotherapy involves taking a medication, by mouth or IV, that targets tumor cells.
Temozolomide (Temodar) is the most commonly used oral medication fo9r astrocytoma.
Side effects of chemotherapy can include nausea/vomiting/decreased appetite, fever, weakness, hair loss. Severity of effects usually depends on dose and type of drug administered.
Tumor Treating Fields (TTF) Therapy
This type of therapy is used either together with chemotherapy or after radiation therapy, and utilizes the electrical field to disrupt the growth of cancerous cells. During this treatment adhesive pads will be applied on the shaved area of your scalp, corresponding to tumor location and the electrical field will be distributed from a wearable device called Optune.
Prognosis, Follow-up, and Rehabilitation
The most important factor for prognosis is a tumor grade. Low grade tumors, such as pilocytic astrocytomas or diffuse astrocytomas have good prognosis with longer survival, compared to aggressive tumors such as glioblastoma multiforme. Your prognosis will be a part of the pre-/post-treatment discussions with your medical team.
During the treatment course you will be under close observation by your medical team. You will have regular check-up appointments, and routine scans will be made to check response to treatment.
Depending on the postoperative course and area of the brain that was involved, you may acquire some deficits, such as vision, balance, motor changes etc. In that case occupational/physical therapy specialists will be involved to speed your recovery and assist in functional restoration.