When cancer spreads from its original location to other parts of the body, it has metastasized. Central nervous system metastases occur when cancer cells spread from their original site to the brain and spinal cord. 

Any cancer can spread to the central nervous system, but the types most likely to cause such metastases are lung, breast, colon and kidney cancers, and melanoma.

Treatment for brain and spinal cord metastases can help ease symptoms, slow tumor growth and extend life. 

To determine which treatment might work best for a person's tumor type, some health care professionals now use liquid biopsies. When a metastatic tumor is in a place in the body that cannot be reached through surgery for a tissue biopsy, liquid biopsies are especially helpful.

A liquid biopsy involves collecting fluid and analyzing it for tumor biomarkers that can help health care professionals determine the tumor's molecular structure and individualize treatment for the best outcome. 

"So we have excellent drugs for different cancer types that are really based off of your specific cancer," explains Dr. Wendy Sherman, a Mayo Clinic neurologist. "So, not just your lung cancer, but does your lung cancer have a specific mutation? And there are drugs that match up to the mutation that have been very effective."

Dr. Sherman explains that halfof the time when a cancer travels to a different part of the body, particularly to the brain, the cancer may change and lose its mutation. 

"So, if you treat someone based off of the information that you had a couple years ago from where the cancer started, that may not reflect the current state of your cancer and what it looks like," says Dr. Sherman. And, so, our treatment really depends on that. And with a lot of these new-generation treatments that are going after these mutations, it has been very beneficial to look for those in the spinal fluid. And it absolutely has improved how people deal with this from a symptom standpoint because we're often able to give them often drugs that are better tolerated because they're more targeted."

Research is underway to further expand the use of liquid biopsies.

"We want to learn more about the use of liquid biopsy, particularly as it pertains to spinal fluid for not just brain metastases but also for cancers that start in the brain," explains Dr. Sherman. "And then also, can we use other fluids in the body? Those samples — urine and blood — are being collected and tested so that hopefully we can make progress toward that use."

On this Mayo Clinic Q&A podcast, Dr. Sherman discusses the use of liquid biopsy in caring for people with breast, lung and gastric cancer that has spread to the brain and spinal cord.