Noninvasive Brain Tumor ‘Surgery’

Dr. Leon Liem
Assistant medical director and neurosurgeon with Gamma Knife Center of the Pacific

Where did you receive your schooling and training?

I did my undergraduate training at MIT in electrical engineering. My medical training was at Albert Einstein College of Medicine. I completed a residency in neurosurgery at University of Maryland.


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Dr. Leon Liem

How long have you been in practice?

I have been a practicing neurosurgeon for 18 years.

What got you interested in the field of neurosurgery?

First, my father was a practicing neurologist and exposed me to medicine and, in particular, the neurosciences. With an engineering background and interest in technological solutions to problems, neurosurgery was a natural fit, since it is one of the most technologically challenging fields in medicine. I was fortunate to have several mentors in neurosurgery who have encouraged me to continue in this field.

What is the Gamma Knife Center and what conditions does the center treat?

We have had the Gamma Knife Center of the Pacific here in Hawaii since 1998. Gamma Knife radiosurgery is a treatment option that was invented by a neurosurgeon, Dr. Lars Leksell, in Sweden. His revolutionary idea was to utilize radiation beams in a precise and accurate manner akin to the precision of microsurgery. Radiation beams cannot be seen or felt, so this technique is essentially noninvasive. Treatments are done as outpatient procedures. Most treatments are completed in a single session. It is a safe technique, with few side effects or complications. A team of a neurosurgeon, a radiation oncologist, a radiation physicist and specialized nurses perform the procedure.

There are now many well-proven applications for the Gamma Knife. Brain tumors, both arising from the brain itself or tumors which arise elsewhere in the body that spread to the brain (metastatic tumors) can be treated. Both benign tumors and malignant or cancerous tumors can be treated effectively.

Additionally, abnormalities in the blood vessels in the brain, including arteriovenous malformations, can be treated with the Gamma Knife.

In many cases, the Gamma Knife obviates the need for invasive open neurosurgery, which carries significant risks. Gamma Knife also is a very good treatment option for patients with trigeminal neuralgia, a very painful and potentially debilitating condition involving the face that is often very difficult to treat with medications. Other conditions that can be treated with the Gamma Knife include movement disorders like tremors and certain chronic pain conditions. New applications are continuing to be explored, including treatments for patients with epilepsy and certain psychological problems. There is continuing active research in these areas.

What did traditional treatment look like for brain metastases before Gamma Knife technology?

The detection of brain metastases — which are tumors that have spread from a tumor in another location in the body — in the past, was a very grim finding. Performing surgery to remove the metastases did show some improvement, but had significant risks. The use of a type of radiation therapy that delivers radiation to the whole brain also can help. But since radiation is delivered to the entire brain, a substantial amount of normal brain can be affected as well. We have found that, as cancer treatment has improved, patients have longer survival.

The effects of the radiation on the brain with whole-brain radiation can result in significant cognitive problems, which can affect quality of life.

There has been a growing shift in treating brain metastases with stereotactic radio-surgery such as the Gamma Knife. We have found that this is a very effective treatment. Many times traditional surgery can be avoided. By avoiding or delaying the use of whole-brain radiation, less cognitive problems are seen. With all the treatment options available for brain metastases, fewer patients are succumbing to the disease in the brain. This allows for a more aggressive treatment of the primary tumor and overall improved patient outcomes.

Any technological advancements in the past five years?

Yes, especially in the area of multiple brain metastases. In the past, if there were four or more brain metastases, Gamma Knife radiosurgery was not recommended. Recent studies have shown the benefit of treatment of more than four and even many more metastases. Treatment of multiple lesions in the brain was often tedious and uncomfortable for patients.

The Gamma Knife Center of the Pacific upgraded the unit to the newest and most sophisticated Gamma Knife, called the

Perfexion. This was not a simple endeavor, since the device weighs about 17 tons. The Perfexion unit treats an unlimited number of metastases in an automatic fashion. This has allowed us to treat multiple brain metastases more efficiently and with improved patient comfort. Patients who were previously treated with whole-brain radiation because of too many metastases now easily can be treated with the Perfexion Gamma Knife. Other conditions are also more efficiently treated on the Perfexion unit.

Anything else you’d like to mention about the Gamma Knife Center?

We are fortunate to have this state-of-the-art medical treatment available for patients in Hawaii. We also have made it available to patients from Australia, New Zealand and Asia. We are excited about the prospect of new, emerging indications for this noninvasive technique.

For more information, call 535-1579 or visit