Brain Metastases: Description And Treatment

Brain metastases are the most common types of brain tumors and they are something of a feed for doctors. They actually contribute about 90% of the total cases of brain tumors.

Estimates indicate that between 10 and 40% of cancer patients have brain metastases. This is because the incidence of them is growing, given the higher average survival of cancer patients, thanks to modern therapies.

Tumors have a different ability to metastasize to the brain and the ability to penetrate the blood-brain barrier, which is because they use it to cover and protect the brain.

Metastasis is a trait that all cancer cells possess, which consists of the ability to invade both near and far tissue from the first tumor. This means that cancer cells can migrate to other parts of the body and cause another tumor.

The clinical metastases in the brain vary and depend on the affected area, as well as the associated risks of seizures.

Causes of brain metastases

Brain metastases usually occur through hematogenous transmission. This is because cancer cells in the primary tumor enter the bloodstream and reach the brain where they spread.

In that sense,  it is interesting to note that the spread of brain metastases is proportional to the blood flow in the affected area. It is placed in relation to the following percentages:

• 80% of lesions in the brain
• 15% in the cerebellum
• 5% in the brainstem

The first step in spreading the cells through the brain is to invade the artery walls at the level of the first primary tumor. That way, some cancer cells can enter the bloodstream.

Then, the cell or cells that entered the bloodstream must be able to attach to the vessels in the brain by penetrating the blood-brain barrier.

The blood-brain barrier and the absence of a lymphatic system provide the brain with significant protection against the penetration of many drugs and microorganisms, but over time it is unable to prevent the penetration of certain cells.

How does the blood-brain barrier cross the neoplastic cells?

The mechanisms used by neoplastic cells to cross the blood-brain barrier are worth studying. However, it has already been proven that there are at least two mechanisms:

• Paracellular. It is to cross between the cells that form part of the barrier. In order to do so,  the cells must destroy the joints between the cells and must have certain proteins and inflammatory mediators.
• Transcellular – this causes direct death of brain cells.

What happens after they cross the blood-brain barrier?

Once inside the brain, the cells pass to the microvasculature of the brain and from there they are spread out, for example, they move towards the tissues.

Survival and spread from that moment on depend on the ability to maintain an adequate supply of oxygen and nutrients,  which explains why these malignant cells stay very close to the blood vessels.

Treatments of brain metastases

Regarding the specific treatment of brain metastases, we can mention the following options:

• Segment resection: This involves removing the tumor through small incisions. It is done through a virectomy and has a number of benefits such as being able to remove the effects of the mass, eliminate the source of edema and improve the overall likelihood of survival compared to holocranial radiation therapy alone.
• Holocranial Radiation Therapy:  Historically, this form of treatment has been considered the best treatment when the tumor is large. It has also been shown to be useful as a contribution to surgical treatment, where it significantly reduces the incidence of recurrences after resection.
• Stereotactic radiation surgery:  This consists of focal beam radiation. It has shown better survival and fewer recurrences in patients with injuries. It can also be better controlled, but there is not a significant difference in the survival rate in people with 2 or 3 lesions.

• Chemotherapy:  Brain metastases are usually quite resistant to chemotherapy. However, the integration of new treatment methods, such as agents to target specific areas and inhibitors of immune control points, has intensified research in this area.

Conclusion

Brain metastases make up about 90% of the total cases of brain cancer. It is therefore essential to make a diagnosis as early as possible in order to try to stop the development of this disease.

There are currently many different treatments and their prognosis is constantly improving. However, brain metastases are a very aggressive type of cancer and there is still a lot of research to be done.

Thanks for reading.