National Brain Tumor Awareness Month is in May of each year. Doctors classify brain tumors as either primary or metastatic. Primary tumors are those that started in the brain or spinal cord. These can be malignant (cancerous) or benign (non-cancerous). Metastatic brain tumors develop when a cancer that started in another part of the body spreads through the bloodstream into the brain. These metastatic tumors are ten times more common than primary brain tumors. I wrote a previous blog on the numerous treatments available for patients with metastatic brain tumors that you could review for more details on that subject. This blog post will be to provide more information on the primary brain tumors not previously discussed.
What are primary brain tumors?
Doctors also refer to primary brain tumors as primary Central Nervous System (CNS) tumors. The CNS includes the brain, spinal cord, and the meninges, which is a protective and supportive layer of tissues surrounding the brain and spinal cord. These primary tumors have started here in the CNS. They are an abnormal growth of cells that can push or invade surrounding normal areas.
How common are primary brain tumors?
According to the National Brain Tumor Society, nearly 89,000 Americans will be diagnosed with a primary brain tumor in 2022 (63,000 will be benign tumors; 26,000 will be malignant tumors).
What is the difference between benign and malignant primary brain tumors?
There are an extremely large number of different types of CNS tumors, likely over 100, so answering questions like this concisely and accurately is challenging. Some generalizations about benign and malignant tumors can be made though. Malignant brain tumors tend to grow faster and have the ability to invade adjacent normal tissues of the brain. Benign tumors tend to grow very slowly and can push on adjacent normal tissues but do not invade them.
What are some of the more common types of primary brain tumors?
Pathologists used to classify these tumors based solely on their appearance when looking at the cells under the microscope. Recent advances in our knowledge of primary brain tumors are reflected in the 2021 release of the WHO CNS 5th edition classification system, which now also uses molecular features to classify the type of tumor. Common examples of malignant primary brain tumors in adults would include glioblastoma (GBM), IDH-mutant astrocytoma, and IDH-mutant and 1p/19q co-deleted oligodendroglioma. In the new system, these tumors also have a numerical grade assigned within their subtype ranging from 2-4. Higher-grade tumors are more aggressive and faster-growing. By far the most common benign primary brain tumor is a meningioma. As you can guess from its name, this type of tumor arises from the meninges (lining around the brain). Other benign tumors we sometimes treat include vestibular schwannomas and pituitary adenomas.
What are the symptoms of a brain tumor?
Some brain tumors are entirely asymptomatic for a long time and may only be diagnosed incidentally on a scan done for some other reason. Other brain tumors do cause symptoms such as frequent headaches, seizures, or a new focal neurologic symptom. Focal neurologic symptoms would include things such as a new arm or leg weakness, a facial droop, worsening coordination, trouble with balance, vision changes, speech difficulties, and memory issues. As you can see, many of these can also be symptoms of a stroke. For that reason, new neurologic symptoms such as these should prompt an immediate evaluation at the emergency department. With modern stroke care, many permanent deficits can be prevented with early detection and treatment. Sometimes the “stroke work-up” in the ER does not show a stroke and instead shows a tumor.
What tests are done to evaluate a brain tumor?
Many patients first have a head CT scan. If anything is abnormal on the CT scan or if the patient’s symptoms cannot be explained by any CT findings, the patient will undergo an MRI. MRI scans are the most sensitive study to evaluate brain tumors and provide much more accurate information about the location and extent of the tumor. Sometimes if the imaging shows a brain tumor, the patient may undergo scans of the remainder of the body (possibly CT scans) to look for other evidence of cancer. As mentioned before, metastatic brain tumors are much more common than primary tumors, so often a source for the brain tumor is found elsewhere (for example, the patient has undiagnosed lung cancer). On the other hand, primary brain tumors do not spread outside of the brain. Some brain tumors are so characteristic on imaging (i.e. meningioma) that the diagnosis is based on imaging alone without a biopsy in many cases. However, we often do not know the type of tumor we are dealing with until surgery is performed and a pathologist can look at the tissue under the microscope and perform additional molecular tests as indicated.
What are the treatment options for primary malignant brain tumors?
Patients generally undergo surgery first. The purpose of the surgery is two-fold. It is a diagnostic procedure that provides the tissue necessary to know what type of tumor is present and what further treatments are needed. It is also a therapeutic procedure to remove as much of the tumor as is safely possible based on the location. We often talk about the concept of maximal safe resection, which could mean a small biopsy alone, removing a portion of the tumor, or removing all visible tumor entirely depending on the location in the brain. Some parts of the brain are too sensitive to remove a portion without leaving patients with significant long-term problems, such as paralysis.
Once we know the type of tumor and the extent of resection, we can determine whether any additional treatments are necessary. Some more favorable low-grade tumors that are completely resected can be observed closely without further treatment. Other types of tumors may warrant either radiation and/or chemotherapy after surgery.
Radiation for primary malignant brain tumors is generally delivered with fractionated treatment over 5-6 weeks (25-30 sessions). These treatments do not target the entire brain. Treatments are instead accurately shaped and targeted to the area around the known brain tumor and/or surgical cavity. Some patients will also receive chemotherapy along with radiation. The drug most commonly used is called temozolomide, which is an oral pill taken at home. Tumor-treating fields (TTF) is a treatment type sometimes employed in the treatment of high-grade gliomas after surgery and radiation. TTF involves a wearable device that administers mild electrical pulses through the scalp that cannot be felt by the patient but can interfere with the cell division of the tumor cells.
What are the treatment options for benign tumors of the brain?
There are many different types of tumors and situations so it is difficult to generalize in a short response. Most small asymptomatic benign neoplasms can be observed with serial MRI scans. Many of these will never grow enough to become symptomatic and require treatment. Some benign tumors do require treatment either because of symptoms being caused due to a tumor in a given location and/or the size of the tumor means the likelihood of developing symptoms at some point is high enough that we need to act. Some benign neoplasms are surgically resected and do not require any post-operative radiation. Other patients may be treated with radiation instead of surgery because the location of the tumor or the patient’s other health problems make surgical resection high risk.
We treat many benign neoplasms with a type of radiation called stereotactic radiosurgery (SRS). These treatments are delivered using sub-millimeter accuracy and precision so we can safely deliver all the treatment in only 1-5 sessions, which are done as an outpatient and do not require any anesthesia or incisions. We do still sometimes use fractionated treatment over 5-6 weeks for benign tumors if the target is too large and/or very close to a sensitive normal structure. To make it a little more complicated, there are also situations where patients have surgery and then still undergo radiation after surgery to minimize the risk of regrowth based on certain pathologic features or imaging findings. These are all situations to discuss with your healthcare team.
What happens after the completion of all planned treatment?
The follow-up for patients with brain tumors includes periodic neurologic exams with their radiation oncologist and/or neurosurgeon. There is also periodic imaging, generally with MRI scans of the brain. The frequency of the scans and follow-up depends on the type of tumor. For malignant brain tumors, patients may undergo these evaluations every 2-3 months. For benign tumors, imaging every 12 months is often sufficient.
Where can I find more information?
The following links have additional useful patient information on this subject and provided some of the statistics for this post.
If you were diagnosed with a primary or metastatic brain tumor and would like to discuss treatment with one of our expert physicians, please contact our office at 256-319-5400 to schedule a consultation.