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Radiation Therapy with Gamma Knife

  • A machine that focuses radiation with precision, killing tumors without harming nearby tissue
  • For patients with good treatment options who want to preserve existing brain function
  • The latest research is changing standards and may make gamma knife available to more patients
  • Involves gamma knife center, interventional radiology

Radiation Therapy with Gamma Knife


The Gamma Knife is a noninvasive, incredibly precise tool for administering radiation, usually to brain and skull-base tumors, blood vessel abnormalities and cases of neuralgia. 

Doctors are able to meticulously focus the radiation, destroying tumors without harming nearby tissue in one of the body’s most sensitive spots—the brain.

The Yale Medicine Gamma Knife Center sees a high volume of patients and has for many years. "That has given us depth and breadth of experience, even in rare cancers," says James B. Yu, MD, co-director of the center.

What types of patients can benefit from Gamma Knife Stereotactic radiosurgery?

Gamma Knife radiosurgery can be of great benefit for patients with good treatment options, a high likelihood of long-term survival, and who want to preserve existing brain function.

Yale Medicine physicians carefully consider a patient’s entire prognosis when deciding whether or not Gamma Knife radiosurgery can be beneficial. 

“We are no longer nihilistic about brain metastases,” Dr. Yu says. “It’s more about how well the cancer is controlled and about a patient’s performance status, how they are doing. A patient may have a dozen lesions, but if the prognosis is otherwise good, Yale Medicine doctors can still select this targeted treatment as the best option.”

How does Gamma Knife radiosurgery work?

The Gamma Knife projects dozens of streams of radiation. On its own each of these streams is not strong enough to damage the brain. However, when the rays meet at the precisely defined area, their collective strength becomes powerful enough to break down a tumor.

What should a patient being treated with Gamma Knife radiosurgery expect?

During the course of care at Yale Medicine, patients will see a radiation oncologist and a neurosurgeon. Typically, a patient will fast overnight before treatment and arrive early in the morning for therapy. The first step involves numbing four spots on the patient’s scalp. The neurosurgeon then attaches a stereotactic frame to his or her head. From the patient's perspective, this process is not unlike the preparation for dental work. 

Patients then get a magnetic resonance imaging (MRI) scan and wait while the treatment team evaluates the scan. The treatment plan is put together with the aid of a medical physicist, who charts how the Gamma Knife’s rays will move through the skull and tissue and arrive at their target.

Administration of the treatment can be as brief as 10 minutes or it can take as long as four hours (if there are a few dozen tumors). The average length of the treatment is about 45 minutes. Because the room is quiet and calm, patients sometimes fall asleep. After treatment, the stereotactic frame is removed. Since no general anesthetic is administered, the patient can return home immediately.

In the following weeks and months, doctors use MRI to scan the area and monitor the tumor’s growth. In the best case, the tumor shrinks over time, never to return. In other cases, a scar remains or the tumor may even endure. Radiosurgery is considered "successful" if a tumor never grows again. 

What other treatments are used in conjunction with Gamma Knife radiosurgery?

There is growing evidence that radiation may improve the body’s immune response, so doctors at Yale Medicine have been working to combine radiation with immunotherapy drugs in order to fight cancer. “You deliver a high dose of radiation to a tumor, and you may be able to cause more antigen presentation,” Dr. Yu says. In other words, the radiation kicks the immune system into overdrive, helping it attack cancerous cells.

Despite promising results, trials are still underway to help answer the unanswered questions in this field, such as: What types of cancer have the best response? How soon after immunotherapy do you have to give the radiation? What’s an ideal dose? 

How is Yale Medicine’s approach to Gamma Knife surgery unique?

"We are now at the forefront of the movement to treat multiple metastases—more than five lesions—with the Gamma Knife, something we would not have thought possible some years ago," says Dr. Yu.

The other cutting-edge area is in the treatment of noncancerous medical problems, such as trigeminal neuralgia and essential tremor, thanks to the precision of the Gamma Knife in training its beams on very specific spots. In addition to patient care, Yale Medicine focuses on academic research, paving the way to breakthroughs large and small. 

Says Dr. Yu: "Where once the application of clinical research to patient care could be quite slow, now we’ve got momentum to apply the latest understanding of conditions and technology as soon as we’ve mastered them. We are the ones generating the evidence and translating the newest discoveries into practice.”