How lasers are attacking 'inoperable' brain and spine tumors

When Allison Easley awoke one morning with soreness under her right armpit, she thought she’d pulled a muscle. But the pain soon became worse, and her lymph nodes started to swell.

“I wondered if I’d caught an infection from one of the kids,” says Easley, 29, a special events photographer who days earlier had taken class portraits at an elementary school.

Antibiotics prescribed by her family doctor didn’t help, and when her pain became unbearable, Easley, who lives just north of San Antonio, visited her local emergency room. Doctors there did a lymph node biopsy and found melanoma, the deadliest form of skin cancer. It wasn’t Easley’s first encounter with the disease.

Ten years earlier, at age 19, she’d been diagnosed with melanoma when a suspicious-looking mole alerted doctors to the disease. They surgically removed it, allowing Easley to live cancer-free for almost a decade.

But now, the melanoma was back with a vengeance. Imaging scans revealed thirty tumors scattered throughout her body. Within months, six would spread to her brain.

“The possibility I’d relapse was always at the back of my mind,” Easley says. “When you’ve had cancer, you’re always waiting for the other shoe to drop.”

Her cancer had been spreading swiftly and silently, and was now stage 4 — the most advanced form of the disease.

This time, Easley sought care at MD Anderson, where doctors prescribed chemotherapy, radiation and powerful new immunotherapy drugs that rallied her immune system and helped her body fight hard. The drugs eliminated all Easley’s tumors — except those in her brain.

“A protective network of blood vessels known as the blood-brain barrier prevents foreign substances from crossing into the brain, but it also can prevent life-saving drugs from entering,” says Ganesh Rao, M.D., associate professor of Neurosurgery at MD Anderson’s Brain and Spine Center.

Brain surgery to remove Easley’s tumors seemed like her only remaining option, but there was a problem. A particularly large tumor had embedded itself deep in the center of her brain, between the right and left hemispheres. Any attempt to reach it surgically would most certainly damage areas that control motor skills affecting coordination and movement.

“This is the juncture where many doctors tell patients their condition is inoperable,” says Rao. “But at MD Anderson, we have another way to reach unreachable tumors.”

Turning up the heat

The cancer center is one of a select few in the nation using a probe that’s specially designed to heat and destroy brain and spinal cord tumors — regardless of their size or location. The treatment is known as laser interstitial thermal therapy, or LITT. Put simply, the name means that laser heat penetrates interstitially — inside tissue — to destroy tumor cells.

“Many types of tumors previously thought to be inoperable can be treated with this technology, including aggressive tumors that originate in the brain or spinal cord, or tumors that have spread to the brain or spine from other areas of the body,” says Sujit Prabhu, M.D., a professor of Neurosurgery who works side by side with Rao in the Brain and Spine Center. “We’re visited by a lot of patients from around the world who’ve been told nothing can be done. We offer them LITT.”

How it works

To perform the procedure, surgeons first study MRI scans of the patient’s brain to create a map of coordinates they’ll follow as they navigate the probe through the brain and into the tumor. The patient is then put to sleep with general anesthesia and placed inside an MRI machine that’s open on both ends.

Next, a dime-sized hole is drilled in the patient’s skull, and the probe is inserted into the brain.  Guided by the previously mapped coordinates, the surgeon carefully advances the probe through the brain and into the middle of the tumor. Because the probe is no wider than a pencil lead, it creates the tiniest of tunnels.

“Tissue damage is nil or close to nil, nothing like that caused by surgical instruments,” says Prabhu.

With the probe in place, the doctor fires a laser beam from its tip. Intense heat emanates from the laser and destroys the tumor’s cells.

“Each burst lasts anywhere from 30 seconds to a few minutes and generates heat ranging from 158 to 176 degrees Fahrenheit,” Rao explains. “It ‘cooks’ the tumor from the inside out.”

Because the patient is continuously imaged inside the MRI, the surgeon can watch the tumor destruction on a monitor as it’s happening. With each firing of the laser, the tumor turns green, yellow, orange, then red as it becomes increasingly hotter. Temperatures are displayed on-screen, confirming that the targeted tissue is thoroughly “cooked” and dead.

Multiple passes with the probe can be made for larger tumors.

“The system knows to burn precisely to the edges of the tumor without crossing over into healthy tissue,” Rao says. “A built-in, emergency off switch engages automatically if the laser heat starts going where it shouldn’t.”

The key to success, Rao says, is achieving the right temperature in the right spot.

“With this technology, we have that assurance,” he says. “We watch the cancer cells on-screen as they’re dying.”

After Rao used the procedure on Easley eight months ago, five of her six brain tumors vanished, and the sixth — the troubling one buried deep in her brain — has shrunk to a fraction of its original size.

“I return to MD Anderson every three weeks for scans, and each time the tumor has shrunk a little more,” she says. “Pretty soon, it won’t be there at all.”

Read more about LITT in MD Anderson’s Conquest magazine.