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The blood-brain barrier is a natural defense system that prevents harmful substances in the blood from entering the brain. Doctors may have found a way to get past the barrier to treat cancer patients.

Neurosurgeons have been using lasers to treat brain cancer since 2009, but now they say the technique may also allow them to deliver chemotherapy drugs directly into the brain.

The key is getting past the protective blood-brain barrier, which does its job so well it also keeps out potentially lifesaving chemotherapy drugs.

Kathy Smith has ovarian cancer that spread to her brain, a type of brain cancer called glioblastoma.

“There were I believe three tumors at that time and I was not at all happy about those critters,” she said.

Smith was treated with laser therapy. Doctors insert a tiny probe into the brain, directly to the cancer where it burns up the tumor from the inside out.

According to Washington University Neurosurgery Professor Eric Leuthardt, during the procedure it was discovered the therapy had an unintended effect on the blood-brain barrier.

“We were able to show that this blood-brain barrier is broken down for about four weeks after you do this laser therapy," he said. "So not only are you killing the tumor, you are actually opening up a window of opportunity to deliver various drugs and chemicals and therapies that could otherwise not get in there.”

In Kathy's case, a powerful, experimental chemotherapy drug called doxorubicin, which has been notoriously hard to get past the barrier was delivered directly into her brain.

“What is interesting is the blood-brain barrier is a two-way street," said Eric Leuthardt. "By breaking it down you can get things into the brain, but also by breaking it down, now things can go from your brain out into your circulation, to your peripheral system, which includes your immune system.”

And the immune system helps fight cancer.

The procedure is dangerous, a compromised blood-brain barrier puts the brain at risk, but so far it has worked well for Smith. Patients diagnosed with glioblastoma tumors usually survive just 15 months after diagnosis.

But Smith has been fighting her cancer since 2009.

“Kind of makes you smile when they say you are a good candidate for something new," she said. "So I got worked into that study and it did work out beautifully.”

The team of neurosurgeons, from Washington University in St. Louis are hoping to publish a more formal report on their work later this year.

Vocabulary

blood-brain barrier: 血腦屏障

（來(lái)源：VOA 編輯：Julie）