As technologies and techniques have advanced in recent years, Gamma Knife radiosurgery has become a vital tool for enhancing outcomes among patients with brain tumors and other complex neurological disorders. Penn State Health Milton S. Hershey Medical Center recently reaffirmed its long-standing commitment to provide the most advanced care in the region by upgrading to the latest iteration of the Gamma Knife radiosurgery system: Leksell Gamma Knife®Icon™.
During the past decade, Hershey Medical Center’s multidisciplinary team has performed more than 1,500 procedures using Gamma Knife technology. In October 2016, the team of 12 physicians and specialists and staff welcomed the future of stereotactic radiosurgery and performed the first procedure with Gamma Knife Icon.
Unlike whole-brain radiation therapy, stereotactic radiosurgery precisely delivers a high dose of radiation directly to the target, sparing healthy tissue from damage. The treatment better preserves patients’ quality-of-life and reduces the likelihood of cognitive-related side effects, according to The ASCO Post, a partner organization of the American Society of Clinical Oncology. Additionally, a 2016 study published in Cancer found that patients with metastatic breast or non-small-cell lung cancer who had fewer than four brain lesions and were treated with stereotactic radiosurgery had longer survival rates than those who underwent whole-brain radiation therapy.
Gamma Knife Icon has multiple advantages. For instance, the technology offers both frameless and frame-based immobilization, allowing for easier, more comfortable fractionated treatments. Gamma Knife Icon also offers a high level of precision — 0.15-millimeter accuracy, a measure that is six times better than industry standards, according to developer Elekta. Finally, Gamma Knife Icon features specialized techniques for enhanced dosing control and motion management, as well as a built-in cone beam CT.
“Gamma Knife Icon’s cone beam CT allows physicians to perform a quality assurance check prior to initiating the predetermined treatment plan, to make sure nothing has changed,” says Heath Mackley, MD, FACRO, co-director, Penn State Gamma Knife Radiosurgery Program. “While I don’t anticipate treatment adjustments happening often, this feature provides an additional layer of safety that is beneficial even for framed cases. The technology expands candidacy for radiosurgery.”
Comprehensive Care for Benign and Malignant Brain Tumors
Gamma Knife radiosurgery may be part of the treatment plan for benign brain tumors, such as meningiomas, acoustic neuromas and pituitary adenomas.
“Most patients with any of these tumors are first referred to a neurosurgeon, before involving radiation oncology,” says Leonard C. Tuanquin, MD, medical director, Division of Radiation Oncology at Hershey Medical Center. “Neurosurgeons then refer patients to radiation oncologists for radiosurgery treatment options, if and when appropriate. As an example, for treatment of acoustic neuromas, options include surgical resection, as well as observation to ensure minimal growth. To prevent further growth, radiosurgery is considered.”
While radiosurgery is used less frequently in the treatment of primary malignant brain tumors, it is often used to manage melanoma, colon, lung or breast cancers that have metastasized to the brain – a prime example of the importance of the multidisciplinary, comprehensive care team involved in each patient’s diagnosis and treatment. Patients who have metastatic cancer or other complex disorders benefit from the expertise of neurosurgeons, neuro-oncologists and radiation oncologists from Penn State Cancer Institute and Penn State Neuroscience Institute. The team meets regularly for tumor boards and coordinated treatment planning for these patients. Depending on the diagnosis, a variety of therapies may be utilized.
“ Ten years ago, survival outcomes for metastatic brain cancer were quite poor. Today, people are living longer. The beauty of referring patients with metastatic brain disease to a center that offers the full range of therapy is that optimal treatment courses can be designed for each patient without limitations related to technology or expertise.”
— Brad Zacharia, MD, MS, director, neuro-oncology and skull base surgery, Penn State Neuroscience Institute, and co-director, neuro-oncology, Penn State Cancer Institute
“We have many tools in our armamentarium for management of these tumors, which is why a multidisciplinary team is required to offer tailored care,” says Brad Zacharia, MD, MS, director, neuro-oncology and skull base surgery at Penn State Neuroscience Institute, and co-director, neuro-oncology at Penn State Cancer Institute. “From a surgical standpoint, we typically operate on patients with neurological symptoms, such as weakness or seizures, who have large tumors resting on critical areas of the brain. In these patients, surgery ameliorates neurological symptoms and provides the best chance of oncologic control.”
Chemotherapy and radiation therapy may then play roles in treatment. Whole-brain radiation therapy had been the gold standard option in the past. While this therapy is still used to treat some patients with many small lesions or surgically inaccessible lesions, this technique exposes healthy brain tissue to high amounts of radiation. For this reason, the precision of Gamma Knife radiosurgery has gained favor over whole-brain radiation therapy in recent years. Now, Icon allows experts to target areas once considered too risky even for radiosurgery. With unprecedented accuracy, Icon now enables treatment of tumors close to critical brain structures.
Traditionally, Gamma Knife radiosurgery has been administered as a single-dose treatment and used to treat cancers with four or fewer metastases. Because of enhancements unique to Gamma Knife Icon, however, the technology may be used to treat upwards of nine or 10 lesions during the course of as many as five treatments delivered over a week and a half.
“With the older versions of Gamma Knife, it was more labor-intensive to move from one target to the next and more challenging for patient comfort,” Dr. Mackley says. “The longer patients had to lie still on the table, especially with the frame, the less feasible the procedure became. Gamma Knife Icon gives us two advantages that make it easier for patients. One is the ability to move from target to target seamlessly, while the patient is on the table. The process is very quick and requires no manual labor. The other advantage is for patients who need a fractionated or lengthy treatment — up to three hours or more — we can use the frameless option for immobilization.”
“Gamma Knife Icon allows us to continue safely, effectively and precisely targeting intracranial brain tumors with radiosurgery. In addition, it gives us the flexibility to perform fractionated radiation treatments — while still ensuring the high precision of therapy — to target larger brain tumors that otherwise cannot be treated with single-fraction treatment.”
— Leonard C. Tuanquin, MD, medical director, radiation oncology, Penn State Health Milton S. Hershey Medical Center
Frameless immobilization is achieved through use of a thermoplastic mask that is individually molded to conform to each patient’s anatomy. The cone beam CT attached to Gamma Knife Icon allows physicians to ascertain that patients are in proper position even when they are not completely fixed to the table. The motion management capability also allows physicians to visualize subtle patient movements in real time while patients are wearing the mask.
“If head position is off from where we feel is acceptable, the machine pauses so we can make subtle changes,” Dr. Tuanquin says. “These enhancements help ensure the fractionated treatment is delivered with high-precision accuracy.”
In addition to the ability to perform fractionated treatments, frameless immobilization enhances comfort and convenience for patients. Without this immobilization enhancement option with the new technology, affixing the titanium frame to the patient’s head requires local anesthesia, mild IV sedation, and patients must have a friend or family member drive them to and from their appointment. Frameless immobilization, on the other hand, requires no such sedation and patients are free to drive after treatment.
Managing Arteriovenous Malformations
Abnormalities of the brain vasculature, arteriovenous malformations (AVMs) are relatively rare, affecting less than 1 percent of the population, according to the American Heart Association and American Stroke Association. However, these lesions can significantly undermine quality-of-life. The American Association of Neurological Surgeons lists headaches, seizures, weakness or loss of coordination, memory loss and dizziness among the most common symptoms caused by AVMs.
The experts at Hershey Medical Center offer three treatment options for patients with AVMs: microsurgery, endovascular embolization and radiosurgery. Microsurgery is used to remove small, focal, surgically accessible AVMs via craniotomy. Endovascular embolization uses a catheter to inject embolic agents into the arteries supplying blood to the AVM. This procedure is often used to reduce the size of larger AVMs prior to microsurgery, according to Kevin Cockroft, MD, MSc, co-director, Penn State Comprehensive Stroke Center. The third option — radiosurgery — uses beams of highly targeted radiation to cause cellular changes in AVM vessels.
“Radiosurgery is ideal for treating small AVMs located deep within brain tissue that can’t be treated any other way, and also offers fewer risks,” Dr. Cockroft says. “The technique is noninvasive and doesn’t require manipulating brain tissue.”
“Our greatest strength is our institutional experience. Members of our team have each been involved in hundreds of cases. We have a wealth of expertise to draw on, and we’re excited to bring Gamma Knife Icon to our patients.”
— Heath Mackley, MD, FACRO, co-director, Penn State Gamma Knife Radiosurgery Program, Penn State Health Milton S. Hershey Medical Center
In addition, Dr. Cockroft sees applications for Gamma Knife Icon in the treatment of large, complex AVMs. “In cases where we may have trouble targeting the AVM, we can perform a cone-beam CT scan to recheck the accuracy of our targeting before treatment,” he says. “Dose fractionation may also be beneficial for patients with large lesions. With the former Gamma Knife technology, we performed volume fractionation, in which we irradiated separate parts of the lesion during different treatment sessions that were usually spaced six months apart. Using the new Gamma Knife Icon, we can potentially administer lower doses of radiation and, perhaps, treat the entire AVM during each treatment session.”
Offering Solutions for Trigeminal Neuralgia
For patients who suffer with trigeminal neuralgia, the intense pain from the disorder can greatly disrupt daily activities and diminish quality-of-life. By definition, the disorder is a chronic, neuropathic pain syndrome stemming from irritation of the fifth cranial nerve and most frequently affects women and older adults. The pain — similar to a stabbing sensation or electrical shock — is often felt in the lower face and jaw and is typically intermittent. In the atypical form of the disease, pain may be less severe, but constant. The majority of patients treated at Hershey Medical Center are in their 70s and 80s, according to James McInerney, MD, neurosurgical director, Penn State Gamma Knife Radiosurgery Program.
“Patients with trigeminal neuralgia typically begin treatment with dental work to address the discomfort and pain. If that doesn’t resolve the issue, it’s important to refer patients to a neurologist who can offer a variety of treatment solutions for this painful condition.”
— James McInerney, MD, neurosurgical director, Penn State Gamma Knife Radiosurgery Program
Trigeminal neuralgia has been linked to brain tumors that compress the nerve and multiple sclerosis. In most cases, however, a healthy artery near the base of the brain places pressure on the nerve, which causes irritation, according to the American Association of Neurological Surgeons.
The first-line therapy for trigeminal neuralgia at Hershey Medical Center is medication — usually carbamazepine or gabapentin. If patients do not respond to medications or are unable to take them due to the side effects, surgery is then considered.
“Microvascular decompression, an invasive operation, is the traditional surgical treatment for trigeminal neuralgia,” Dr. McInerney says. “This procedure involves exposing the nerve at the brain stem, identifying the vessel that is impinging on the nerve and repositioning the vessel. This is a tough operation for older adults to undergo, and it can also be more difficult to perform because their vessels may be calcified or atherosclerotic.”
Gamma Knife radiosurgery can be a valuable alternative to surgical treatment. The goal of radiosurgery is to damage the pain signals in the nerve so they are unable to elicit a pain response. As with other diseases, Dr. McInerney notes that the cone beam CT scan, the ability to pre-plan the surgical approach and the frameless option are among the most beneficial advancements of Gamma Knife Icon in regard to treatment of trigeminal neuralgia.
“Previously, we would affix the frame to the patient, take an imaging scan that included the frame and develop a treatment plan,” Dr. McInerney says. “To follow this strict protocol, patients had to arrive early in the morning and travel around the hospital. The new improved options offer greater convenience for patients while providing the most advanced therapy for their relief. Now, with frameless radiosurgery, we can treat them based on a high-resolution MRI obtained prior to their appointment. We can place the frameless mask, perform the cone beam CT scan and initiate treatment. To deliver a 20-minute treatment, the entire process only takes about half an hour.”
Relief following radiosurgery typically lasts five to 10 years, after which the therapy may be repeated.
“Trigeminal neuralgia is very treatable,” Dr. McInerney says. “Our goal is to get people off of pain medications, and radiosurgery is one of the key treatments in achieving that.”
For additional information about Gamma Knife Icon radiosurgery, visit PennStateHershey.org/gammaknife. To refer a patient, call 717-531-8807 and select option 4.