Brain Cancer Metastases - An Overview

Metastasis is the medical term for a complication of cancer when the tumor spreads to other parts of the body. Brain cancer metastases are a cancer that originated from another part of the body, which has spread to the brain. Metastases to the brain are the most common intracranial neoplasms in adults.

The occurrence of metastasis to the brain is on the increase because of the improved survival rate for many cancers. Cancer patients are living longer for a number of reasons; the use of MRI is more widespread and this technique is able to detect and accurately locate small tumors that were invisible in x-rays.

This and other diagnostic techniques are responsible for the detection of cancer much earlier than was previously possible. More sophisticated monitoring processes can now diagnose the recurrence of tumors much sooner than before. Also, there have been significant advances in both diagnosis and management of cancer which has lead to an increased life expectancy.

Around 40% of all intracranial tumors are metastatic, with lung cancer being the most common primary site. Other cancers that metastasize to the brain include, in descending order of frequency, breast cancer, melanoma, renal and colon cancers. Brain cancer metastases are a frightening and dreaded complication of cancer and a major cause of a shortened life expectancy.

In the United States, it is estimated that between 98,000 and 170,000 cases of metastatic brain cancers are diagnosed every year, representing 24% to 45% of all cancer patients in the country. They account for about 20% of deaths from all types of cancer each year.

Early detection and diagnosis are crucial to the survival rate of patients whose cancer has metastasized to the brain. Aggressive treatment can lead to remission of the symptoms of the brain cancer, improve the quality of the patient's life and extend their life expectancy.

The reason that the brain is an easy target for metastatic cancer is the fact that chemotherapy drugs don't penetrate into the brain as easily as to other organs. In addition, the chemotherapy drugs can weaken the blood-brain barrier, making it easy for tumor cells to spread there.

The pathophysiology of metastatic cancer cells is complex; the cells have to get into the blood stream, avoid the antibodies that are out to destroy them and so stay alive while they circulate the body looking for an organ to grow in. They then must pass through membranes into the new organ where they start to grow. Cancer cells are able to produce special enzymes that make all this possible.

Not all cancer cells are the same; some metastasize to a particular organ preferentially because their cells are similar. Scientists think that the final destination of spreading cancer cells is not random, but may actually be guided by the host organ.

Most brain cancer metastases originated in another part of the body; it is rare that a brain cancer metastasizes to another part of the brain. The most common cancer that metastasizes to the brain is lung cancer which accounts for half of all metastatic brain cancers. Of all lung cancer patients who survive more than two years from diagnosis, an incredible 80% will develop brain metastases.