BY DEBBIE GILBERT
When it comes to treating cancer with radiation therapy, "almost" isn’t good enough. If doctors don’t direct the beam exactly where it’s needed, the energy could slice through healthy tissue with disastrous results.
Last month, Northeast Georgia Medical Center began using a new linear accelerator — a machine that delivers radiation — that offers an unprecedented degree of precision.
"It allows us to image the target in almost real time," said radiation oncologist Dr. Frank Lake. "The reason that’s helpful is that the target will move around."
The "target" is a tumor, and sometimes tumors are located in organs that continue to move even though the patient is lying still.
"For example, a lung tumor moves up and down with respiration," Lake said.
Because the tumor is a moving target, in the past doctors had to aim the beam over a fairly wide area in order to make sure they hit it. This meant that even if patients were cured of their cancer, they might be left with permanent damage from radiation.
In recent years, newer technology has allowed doctors to trace smaller margins around the treatment area. With the medical center’s new system, known as Elekta Synergy, the margins can be carved even thinner.
Sometimes tumors also move around from one day to the next. For example, a prostate tumor might be slightly displaced because of pressure from the bladder or intestines. So the new machine recalculates the tumor’s position each time the patient comes in for therapy.
"It has a 3D system that lets us obtain a CT image of the area we’re treating," Lake said. "A special X-ray tube is attached to the machine, at a 90-degree angle to the (radiation) beam."
As if three-dimensional imaging weren’t enough, the machine is also capable of "4D" therapy, an approach that almost pushes the hospital into the Twilight Zone.
"The fourth dimension is time," Lake said. "That translates into movement. We can predict where the tumor will be at any point in time."
That means even if the patient’s breathing keeps the tumor in continuous motion, the beam can still hit it dead-on.
"We expect there will be a lower complication rate," Lake said. "The other benefit is that, because we know the tumor is always under the beam, we’ll have a better success rate (in controlling the cancer)."
With the ability to zoom in on the target, doctors won’t have to be so conservative about the amount of radiation given, because they’re less worried about the beam striking healthy tissue.
"Because there’s less risk of complications, we may be able to go to even higher doses of radiation and give fewer treatments," Lake said.
The hospital’s radiation therapy department already has one relatively new linear accelerator. The latest acquisition replaces a machine that was about 15 years old.
Tom Enright, director of oncology services at the medical center, said the project cost about $2.5 million.
"In addition to buying the machine itself, we had to install a little more shielding in the room (to protect surrounding areas from radiation), and add some more electronics," he said. "This technology is very computer-intensive."
Northeast Georgia Health System has also installed an almost identical linear accelerator at its satellite cancer center in Toccoa.
All the machines will get plenty of usage. Lake said the hospital’s radiation oncology center treats 800 to 1,000 new patients each year, and the number is growing.
"It’s becoming more common for oncologists to prescribe radiation in addition to chemotherapy," he said.