The most common brain tumors are actually metastatic brain tumors, or cancerous tumors from other parts of the body that have spread to the brain. Common cancers that cause brain metastases include breast cancer, lung cancer, renal cell cancer, and melanoma. In fact, brain metastases are nearly twice as common as primary brain tumors, which are tumors that start in the brain itself (have not spread from some other cancerous site).
Each year in the US there will be about 250,000 people diagnosed with a new brain metastasis, as opposed to about 80,000 primary brain tumors. Primary brain tumors include meningiomas, gliomas, pituitary tumors, and other rare tumors that I will discuss in a later post.
Since metastatic brain tumors are cancers that have spread to the brain from some other primary site (lung cancer, breast cancer, kidney cancer, melanoma, etc.), it is postulated that the number of brain metastases diagnosed each year will rise as patients live longer with their primary cancers.
Metastatic Brain Tumors may occur at any site within the brain, and symptoms are based on the location of the metastasis. Since the location of metastatic tumors is highly variable, symptoms experienced may be highly variable. Some common and nonspecific symptoms include headaches, nausea, and vomiting. Seizures may occur due to brain metastases, and these are usually treated with oral medications and removal of the tumor. Finally, neurologic impairment related to the tumor may occur. An example of neurologic symptoms related to a metastasis could be left arm weakness due to an enlarging tumor in the right frontal lobe (the area of the brain related to left arm movement).
Treatment Options for Metastatic Brain Tumors
In general, there are several treatment options for metastatic brain tumors: surgical resection of the tumor, brain biopsy for diagnosis, stereotactic radiosurgery (SRS), whole brain radiation therapy, and post treatment observation and surveillance. Often, patients with metastatic brain tumors undergo some combination of the above treatment options.
Surgical Resection – Large brain metastases may cause neurologic symptoms by compression of the brain or edema (swelling). Surgical resection, or removal of a tumor with surgery, is a common method of treating symptomatic brain metastases. This surgery involves an incision on the scalp, opening of the skull (a craniotomy), and then surgical removal of the tumor. Local tumor control is improved by adding radiation treatment to the tumor bed after surgery is performed and the incision has healed. Resection has the additional benefit of allowing a pathologist to examine the tumor after it is removed, which often allows them to determine the site of origin.
Stereotactic Radiosurgery (SRS) – SRS is a method of high precision radiation treatment for brain tumors, where a very high dose of focused radiation can be directed at one or more tumors. SRS allows high dose radiation to be delivered to a target (tumor) and a relatively small dose to the surrounding tissues. Dr. Lawson performs radiosurgery with local radiation oncologists, and you can learn more about SRS here. There is some evidence that radiosurgery has better cognitive outcomes and equal efficacy compared to whole brain radiation. Check out a recent article in JAMA on the issue here.
Whole Brain Radiation – Sometimes, there are numerous small brain metastases, too small or too numerous for surgical resection or radiosurgery. Whole brain radiation delivers a moderate dose of radiation to the entire brain. This treats both the tumors as well as brain tissues. It is effective, but may have long-term cognitive site effects (this is controversial).
Brain Biopsy – Occasionally, tissue diagnosis is needed for a brain tumor but the tumor is not in a location safe for surgical resection. Stereotactic Needle Biopsy may be a good option for obtaining tumor tissue for analysis and diagnosis. In this procedure, the patient is taken to the operating room and a small needle is passed through the skin, the skull, and into the tumor. This procedure uses computer navigation to accurately direct the needle into the tumor.
The Long Term Plan
In general, treatment of patients with brain metastases requires a team approach, with Neurosurgeons, Oncologists, and Radiation Oncologists. The individual prognosis depends on the patient’s primary cancer, their functional status, and how well they respond to the initial treatments. Dr. Lawson works closely with local TMH oncologists and radiation oncologists to give the most comprehensive brain tumor care in the region.