What is Brain Metastasis? Causes and Treatment

Brain metastases are one of the common neurological complications in cancer patients. According to various studies, its incidence is approximately 9-17%. Brain metastases are the most common type of lesion, occurring 7-8 times more often than primary brain tumors. It is detected in approximately 20-40% of cancer cases.

The most common causes of brain metastases can be listed as lung cancer (36-64%), breast cancer (15-25%), and melanoma (5-20%). Metastatic tumor cells reach the brain and most commonly spread to the cerebral hemisphere (80%), cerebellum (15%), and brain stem (5%). Although the most common complaints of the patients are headache, epileptic seizures are also one of the main reasons for applying to the emergency department.

Who Gets Brain Metastasis?

The incidence of brain tumors increases with age, especially after 30 years of age. Among the causes of brain tumors, genetic factors and environmental factors are reported as a common opinion. Brain tumors are mainly divided into 2 different groups as primary tumors and metastases. Metastases constitute 20-40% of various tumors.

With the availability of advanced imaging techniques that help in early diagnosis and effective life-prolonging systemic treatments, the incidence of cancer spread to the brain is increasing. Lung cancer and breast cancer are the most common tumors that metastasize to the brain, accounting for 67-80% of all metastases.

Most patients with brain metastases also have extracerebral (extracerebral) metastases. Some patients present with a diagnosis of metastasis without a known primary cancer. Brain metastases are rare in children, and germ cell tumors, sarcomas and neuroblastomas are the most common causes.

Brain Metastasis Frequency

Metastatic tumors increase the internal pressure of the head. Pressure increase is the most obvious data. Vomiting, nausea and headache may occur due to increased pressure. In addition, loss of balance, fatigue and weakness, numbness and even seizures may occur. Metastatic tumors are common.

The number of patients with brain metastases is increasing year by year. It is more common than all other brain tumor cases combined. With the development of treatment possibilities in cancer patients, the life expectancy of patients has been prolonged and more brain metastases have been encountered. In autopsies, findings show that 30-40% of patients who die due to cancer have brain metastases.

What Are the Causes of Brain Metastasis?

Among the most important causes of brain metastases are lung cancer in men and breast cancer in women. Cancer cells reach the brain through the blood by passing through the lungs.

Cancer cells in the lung or elsewhere in the body enter the blood vessels and reach the brain by circulation. Since cancerous cells reach the brain through the blood, it encounters more metastases because it is the area of the brain that receives the most blood.

Fewer metastases are seen in the cerebellum and spinal cord. About 80% of all metastases occur in the brain, 15% in the cerebellum, and 5% in the spinal cord. Metastases are usually multiple and the condition is one of the determining factors in how treatment will be.

The Relationship Between Brain Metastasis and Lung Cancer

The most common tumor that metastasizes to the brain is lung cancer. Lung cancer is the most common type of cancer worldwide. In addition, the most lethal type of cancer among cancer types is lung cancer.

According to the data released by the Ministry of Health in Turkey in 2018, lung cancer ranks 5th among the most common cancer types in women. For men, it ranks first. Studies reveal that approximately 35,000 new cases of lung cancer are diagnosed each year.

Although it is known that lung cancer is the most common type of cancer that metastasizes to the brain, the source of metastasis cannot be found in approximately 15% of patients with brain metastasis.

Brain Metastasis Treatment

Many methods are used when treating metastatic tumors. Radiosurgery, chemotherapy and radiotherapy are used alone, especially surgical methods. All these methods can also be used in combination. It is known that metastatic tumors cause the death of the patient within a period of 1 month, on average, if left untreated.

Radiotherapy is the most widely used method in the treatment of metastatic tumors. The growth of tumor cells in the brain can be stopped by radiotherapy. At the same time, tumor cells can be destroyed. Two procedures are performed in the radiotherapy method. First, the tumor tissue viewed in MRI is irradiated. In addition, it is aimed to affect tumor cells that are not seen in MRI during this irradiation.

Some types of tumors, such as breast cancer and small cell lung cancer, are highly sensitive to radiation. Such tumors can sometimes disappear in a very short time after radiotherapy. It cannot be seen during MRI controls performed afterwards. However, some tumors (such as malignant melanoma, colon cancer, kidney cancer, and non-small cell lung cancer) are less sensitive to radiation. In such tumors, it may be necessary to use radiosurgery in addition to radiotherapy. In particular, patients with small cell lung cancer receive radiotherapy for preventive purposes, even if no metastases are detected in the brain in MRI examinations.

Radiotherapy in brain metastases is a treatment method that is becoming more popular due to many reasons such as newly developed techniques, providing a short regression in symptoms, being a procedure that does not require surgical intervention, and providing continuous treatment without the need for convalescence.

Surgical Methods in the Treatment of Brain Metastasis

Preferring surgical treatment as the treatment method for metastatic tumors and removing the tumor by surgical operation prolongs the life span. The surgical method is mostly applied in tumors that are one, large, edematous and cause neurologic regression.

After surgery, additional treatment with radiotherapy is required in patients. In the radiotherapy method, high doses of radiation are directed to a small spot detected in the skull.

Radiosurgery in the Treatment of Brain Metastasis

The biggest advantage of the radiosurgery method is that the treatment can be done in one go. For this reason, radiosurgery method is preferred more in patients whose general health is not good. Thanks to the radiosurgery method, the growth of the metastatic tumor is prevented. The rate of gradual shrinkage and even complete disappearance of the tumor is around 95%. This is the same as the value obtained with surgery. Because of these advantages, radiosurgery is considered the first choice in the treatment of metastatic brain tumors all over the world.

Another advantage of radiosurgery is that it can be applied more than once in case of response to treatment. If tumors occur in different parts of the brain over time in a patient with brain metastasis, radiosurgery can be applied to each tumor as needed. Since the regions of the brain that are not exposed to tumors are not irradiated in radiosurgery, side effects are not observed. For these reasons, in recent years, patients have been followed up with direct and only radiosurgery without radiotherapy. If necessary, radiotherapy is applied afterwards.

Chemotherapy is usually not very effective in brain metastases. However, some studies have shown that chemotherapy prolongs the life span of some tumors.

Early Diagnosis in Brain Metastasis Treatment

Early diagnosis is of great importance in the treatment of brain metastases. Thanks to early detection, brain metastases usually respond to treatment. With early diagnosis and treatment, symptoms are alleviated. Tumor growth is slowed down. In addition, early diagnosis also provides prolongation of life quality and duration. However, it should not be forgotten that tumors may recur after brain metastasis treatment. Which treatment will be beneficial for the patient varies depending on the number, size, location of the tumors, symptoms, other accompanying diseases and the patient's preference.