Using a concentrated dose of radiation precisely delivered to the target brain tumor sans incision, patients who undergo Gamma Knife surgery can resume their normal daily activities the next day.
“We had a doctor before who, after going through the Gamma Knife treatment, did surgery the following day,” Dr. Michael Louis A. Gimenez, neurosurgeon and chairman of the Brain and Spine Institute at Cardinal Santos Medical Center told Manila Standard in a virtual interview.
Gamma Knife surgery is a non-invasive brain surgery that uses specialized equipment to focus about 200 tiny beams of radiation on a tumor to shrink or stop its growth. It can treat both benign and malignant tumors no bigger than 3 to 3.5 centimeters in any location of the brain.
“The lesions that we treat are predominantly brain tumors, abnormal blood vessels in the brain, and even painful conditions like trigeminal neuralgia,” said Dr. Gimenez.
It is an alternative to invasive surgery; ideal for deep-seated tumors, for patients who cannot tolerate open surgery, and for specific indications wherein open surgery may not be ideal or the complication rates are “very considerable.”
“If you have a deep-seated tumor that’s in a deep location in the brain and is causing the patient symptoms, open surgery may actually cause complications because of the deep location of that tumor,” explained the neurosurgeon.
Thus, he said, “Gamma Knife Surgery would be a very effective alternative to control this tumor and limit complications arising from open surgery.”
Dr. Gimenez, however, clarified that while this stereotactic radiosurgery is as effective, if more, as open brain surgery in specific cases, “standard open brain surgery will still have a major role.” This considering one of the limitations of Gamma Knife is that it is only suitable for small- to medium-sized tumors.
“You also need to consider the size in relation to the location,” said Dr. Gimenez. “For example, if you have a 3.5cm tumor in a very deep and eloquent location, that is harder to treat than a 3.5cm lesion in a superficial part of the brain.”
In addition, there are specific types of tumor which are “very responsive” to Gamma Knife, and other types which are more amenable to open surgery or other forms of radiation therapy.
What to expect
Since it is non-invasive, no incision or general anesthesia is involved in the treatment procedure. In fact, the only reason why it’s called “surgery” is because the effects are simulating that of open surgery by using radiation sources to hit specific targets in the brain, according to Dr. Gimenez.
The non-invasive nature of the treatment also allows it to be performed in an outpatient setting where the patients are sent home on the same day.
Although taking liquids or a bit of food is not a contraindication, patients are advised not to eat from midnight until after the treatment. They can, however, take liquids or hard candy, according to Dr. Gimenez. “This is just so they don’t vomit during any part of the procedure.”
The treatment starts with an evaluation of the neurosurgeon, during which a lightweight frame will be attached to the head and will undergo imaging scans that may include magnetic resonance imaging (MRI) or computerized tomography (CT) scan.
Patients allergic to the dye used in MRI or those with medical devices implanted in their bodies must advise their physician prior to the procedure.
After the scanning, the doctors will then plan the treatment to target the lesion and determine the appropriate dose of radiation to be delivered. The patient will then undergo the radiation treatment wherein a frame with pins will be attached to their head to serve as point of reference for focusing the beams of radiation.
Laying out the process, Dr. Gimenez said, “Framing is done in 10 to 15 minutes, after that the patient goes for an MRI which lasts about 30 minutes. The patient is allowed to rest while treatment planning is taking place, which would probably take an hour or an hour and 15 minutes. Finally, the patient is put in the Gamma Knife machine radiation delivery which looks similar to an MRI machine but without the noise.”
“Overall, in half a day you will be able to treat the patient. The treatment time depends on the tumor and type of tumor,” he added.
Their hair will not be shaved prior to the treatment and no hair loss is expected to occur after, because despite the use of radiation, Dr. Gimenez said that “the almost 200 rays come from different directions and converge in one target” thus, each ray will not have the same effect as the convergence where the high dose of radiation is given.
Although common immediate side effects include pain or mild headaches on the pin sites where the frame was placed—“That’s why they (patients) are kept on analgesic for a day or two”—the neurosurgeon reiterated that “they can go back to work the following day.”
“Long-term complications,” Dr. Gimenez said, “are related to radiation treatments.” Thus a patient can have swelling months after or cyst formations. “Radiation-induced effects are usually self-limiting, meaning they usually resolve in time after a couple of months.”
“The long-term lifelong complications are few; a small percentage of patients may have it. But compared to open surgery, they’re much less,” assured Dr. Gimenez.
Success rate
Gamma Knife surgery is safe for children, the elderly, and even for pregnant women. However, while the fetus is not exposed to the radiation focused on the head, the center tries to avoid this treatment for pregnant women “as a precaution.”
Success varies in terms of the type of tumor or type of vascular malformation, but according to Dr. Gimenez, overall success rate for brain tumors is approximately 90 percent.
“Success is defined by shrinkage of these tumors. For malignant tumors they really shrink significantly. For benign tumors, it stops the growth of the brain tumors so that they don’t cause progression of neurologic symptoms usually during the patient’s lifetime.”
At the moment, only the Philippine Gamma Knife Center—one of the eight multidisciplinary centers of the Brain and Spine Institute at Cardinal Santos Medical Center—has the machine used specifically for this procedure. Since 1998, the center’s team of neurosurgeons has performed about 3,500 procedures.
The entire procedure costs P560,000.