Brain metastases are tumors that result from spread of cancer cells from other sites in the body. Overall, they are the most common tumors that occur inside the skull and about 170,000 new cases are diagnosed in the US each year.
Every cancer has the potential to spread to the brain. However, some cancers are more likely to spread to the brain than others. The more common cancers that can cause brain metastases are lung, breast, melanoma, renal and colon cancers. Primary lung tumors are most common originators followed by breast cancers because of the sheer number of cases of these cancers.
The incidence of brain metastasis peaks in the fifth to seventh decades. However, they are uncommon in children because typical cancers causing brain metastases are extremely rare.
The symptoms caused by brain metastases are determined by their size and location. Keep in mind that if there are multiple metastases, there may be a combination of symptoms.
Increased Intracranial Pressure. In many patients, the growth of tumors increase the pressure inside the skull which cannot expand. In addition, tumors can cause swelling as well contributing to the increased pressure. This can cause headache, vomiting, and decreasing consciousness.
- Headache. Headache is a common symptom in about half of patients with brain tumors. Therefore, a new headache, while non-specific, occurring in a patient with a history of cancer must be investigated with imaging.
- Vomiting. When the intracranial pressure is high enough, vomiting may accompany the headache. This is more common in children than adults.
- Altered Mental Status. Depending on the size of the tumor and the amount of associated swelling, a patient’s mental status can change. The symptom may range from simple confusion to sleepiness or even coma.
Seizures. Seizures can be the first symptom of a brain tumor in many patients even without a cancer history. Abnormal movements or sensations can occur in a single extremity or can generalize to the entire body. A first seizure in an adult must be investigated with imaging.
Focal Neurological Deficits. If a tumor grows in regions of the brain that control movement, sensation or speech, more specific neurologic symptoms may occur such as weakness, tingling, or slurred speech.
When a patient presents with any of those symptoms, the initial study of choice is usually a CT scan of the head. CT scans are more useful for looking at bony structures and bleeding. However, they are fast and can pick up large tumors or areas of swelling. The ideal study is a contrasted MRI which is better for looking at soft tissues like brain and tumors. However, these require more time and since it requires the use of magnets, any history of metal implants into the body may complicate matters.
Treatment depends heavily on the type of tumor that is diagnosed. However, factors that may alter treatment strategy include the patient’s age, other medical problems, number of brain tumors, and tumor size. Cancer treatment requires the coordination of many doctors each managing a specific aspect of the treatment. Some tumors respond well to radiation (small cell lung cancer, lymphoma, etc) and surgery may not be indicated unless the tumors are extremely large. Some tumors do not respond well to radiation (non-small cell lung cancer, melanoma, etc) and surgery may be indicated. Typically, treatment plans involve a combination of surgery, chemotherapy, and radiation.