New York Methodist Hospital (NYM) in Brooklyn recently installed a new stereotactic body radiotherapy (SBRT) system and the oncology team can now target tumors anywhere in a patient’s body from almost every angle. Some patients are even able to undergo the procedure in only a few minutes. There are a variety of SBRT and stereotactic radiosurgery (SRS) systems on the market with unique offerings. NYM chose Varian’s TrueBeam Radiotherapy System because it believes it delivers the same high radiation dose rate as the other systems, but can be used to treat a wider range of indications including large-sized cancers and tumors smaller than 1 centimeter.
 
Elekta’s Gamma Knife was specifically designed to treat brain tumors and Accuray’s CyberKnife has a robotic gantry that can be moved in any position. But what all the systems have in common is that hospitals are becoming increasingly interested in the technology. “Both the numbers of patients and the sites being treated with stereotactic radiosurgery are on the rise,” says Dr. Hani Ashamalla, chair of the department of radiation oncology at NYM. “We are currently treating lung, spine, brain, and liver tumors with stereotactic radiosurgery. We anticipate that the number of patients seeking this type of technology will continue to increase, since it delivers very effective and precise doses in a short period of time.”
 
Growing use of SBRT and SRS
Surgeons attempt to remove an entire tumor with surgery, but it’s a very difficult task and oftentimes some of the tumor remains. More surgeons are now turning to SBRT and SRS to remove the remainder of a tumor. “Radiosurgery is very effective for small tumors, but if you just cut up a majority of a large tumor and make the part that is left over small, then radiosurgery can handle that effectively,” says Dr. Lijun Ma, a physicist from the University of California San Francisco radiation oncology department.
 
At first, many surgeons were reluctant to use SBRT and SRS. There have been questions about whether it can cause cancer and if it will make it more difficult to perform surgery afterward. “Skull-based surgeons are really good at what they do and are very proud of their surgical skills,” says Catherine Gilmore-Lawless, vice president of clinical intelligence at Elekta. “Their acceptance of radiosurgery as an integral part of their treatment strategy has been increasing over the last 20 years.”
 
A significant volume of data has emerged about the effectiveness of SBRT and SRS, and more surgeons are being exposed to it in their training programs. It is now entrenched in educational programs at the majority of neurosurgery departments. The fields of surgery and radiation oncology are starting to merge, and cancer treatment is becoming a multi-disciplinary team approach, says Ma. He estimates that 70 percent of the time neurosurgeons are performing surgery in the operating room and 30 percent of the time they’re performing SBRT or SRS.


 
Major workflow improvements
In the past, when a patient came to the radiation oncology department with a tumor, the surgeon would carefully determine how and where to treat them. A dosimetry team would design a plan to make sure the right dose was administered and then quality assurance would be performed after the procedure to make sure everything was done safely.
 
“Workflow has improved night and day over the years,” says Ma. “The SBRT and SRS workflow is totally different from traditional radiation oncology workflow — the patient comes in and you do it quickly. It’s more like a surgical workflow.” In August, Elekta received 510(k) approval from the FDA for its new Gamma Knife system, Icon. Ma believes that the Icon is a paradigm shift and is going to change the way large tumors are treated.
 
Gamma Knife systems traditionally have head frames, which attach to the patient’s head with four small screws and ensure that the radiation beams are precisely targeted. But the Icon system is frameless and uses a cone-beam CT (CBCT) workflow that allows the physicians to check the patient’s position against planning images.
 
During the treatment, patient motion is managed with a motion management system that tracks the patient’s head position. If the patient coughs or moves their head, the system will automatically stop delivering radiation. Other technologies on the market can also account for patient movement. Vision RT’s AlignRT can be used along with the TrueBeam system to customize how much the patient can move before the radiation beam stops, in order to avoid affecting healthy tissue.
 
Accuray’s CyberKnife M6 Series features its new InCise Multileaf Collimator (MLC) that works by precisely sculpting dose to spare healthy tissue, even for targets that move during respiration. “By minimizing dose to the normal and healthy tissue, side effects are minimized and patients benefit in their quality of life as they go through cancer treatment,” says Kelly Londy, executive vice president and chief commercial officer of Accuray. The Icon is also optimized to perform microradiosurgery.
 
During microradiosurgery, the neuroanatomy is very precisely defined and the dose is conformed to the target volume with very high selectivity in order to preserve any normal structures. Microradiosurgery is commonly used by Gamma Knife centers for extremely exacting indications in very critical anatomical locations such as the brain stem, adjacent to the optic apparatus, in the cavernous sinus and for functional disorders like essential tremor. “[These types of cases are] really the toughest of the tough. You have to be absolutely sure of what you are doing,” says Gilmore-Lawless.
 
Microsurgery is also used for trigeminal neuralgia, which is a pain disorder caused by a tiny nerve sticking out of the brain stem. The dose must be manipulated around the nerve, which involves very precise sculpting capabilities in a tight space.
 
New indications for SBRT
Lung SBRT has become routine for treating non-small cell lung cancer tumors (NSCLC), typically less than 3 centimeters in diameter, because of its high rate of local control and limited toxicity. But new research shows that it can also be used to safely treat inoperable NSCLC tumors larger than 5 centimeters. A new study published in the International Journal of Radiation Oncology Biology Physics found that SBRT can treat larger tumors with low rates of recurrence at the primary cancer site with minimal side effects.
 
“There has traditionally been a fear of treating larger tumors with SBRT because it’s really destructive when the high dose of treatment is given compared to most radiation that is given in gentle or smaller doses,” says Dr. Neil Woody, radiation oncologist at the Cleveland Clinic and one of the authors of the study. The researchers evaluated the outcomes of 40 patients 18 months after SBRT was used to treat their node-negative, medically inoperable NSCLC tumors that were greater than 5 centimeters. They found that SBRT can effectively and safely treat those types of tumors.
 
There was no evidence of disease at the original tumor site in about 91 percent of the cases and 32.5 percent of the patients experienced distant failure, which is when the cancer spreads to other parts of the body. Additionally, 70.5 percent of the patients didn’t experience any side effects. When the results were compared to published surgical studies, lung SBRT appeared to have similar rates of local control and distant failure. The median age of the patients was 76 and most of them had several significant comorbidities. The preferred way of treating NSCLC is with surgery, but this group of patients couldn’t handle an invasive procedure.
 
“In our population, these are patients who don’t have that option — their lung function is too poor and their heart function is too poor,” says Woody. Before the emergence of lung SBRT, frail, medically-compromised patients with nodenegative inoperable NSCLC were often treated with external beam radiation therapy, which delivers lower doses over more treatment sessions. However, many of the patients experienced several side effects and the cancer often recurred. Since it was a retrospective study that evaluated only a small number of patients for less than two years, more research will be needed to confirm these results.
 
Mounting research
There used to be a notion that radiosurgery could only treat three or fewer tumors in a patient, but there was no data to support that. A study conducted in Japan and published in Lancet Oncology last year investigated how many tumors can reasonably be treated with radiosurgery.
 
The researchers evaluated patients with two to four brain metastases and patients with five to 10 brain metastases who were treated with SRS at 23 facilities in Japan. They found that there is no difference in results between the two groups of patients. “That study, along with recently updated guidelines and the ASTRO recommendations, is really fueling a change in the way these patients are treated and for the betterment of these patients,” says Gilmore-Lawless. “In the past, patients with largernumbers of metastases would either not be treated or have whole brain radiation therapy and would frequently be viewed as futile cases.”
 
The researchers know that it’s not a number issue, but rather the volume of tumors. Insurance companies are even willing to reimburse cases when patients have more than three metastases, says Gilmore-Lawless. Another area that many studies are looking into is the combined use of radiosurgery and drugs. The health care industry is trying to figure out which drugs are the most effective, whether there are safety issues with the combined use of drugs and radiosurgery, and what the optimal drug strategy is.
 
“There is an emerging belief that radiosurgery could play a role in activating the immune system potentially synergistically with immunotherapy to achieve better results,” says Gilmore-Lawless. “This is a promising new area of ongoing investigation and nobody has the answers here yet.”
 
Era of big data
Health care is beginning to leverage the power of big data. Industry experts believe that analyzing large quantities of data has the potential to improve treatment outcomes and reduce costs. “Radiation oncology, like a lot of other fields in medicine, is just now trying to wrap our collective heads around what to do with some of these enormous information databases that are becoming available in health care,” says Dr. Brian Kavanagh, presidentelect of the ASTRO Fellows Program and interim chair of the department of radiation oncology at the University of Colorado School of Medicine.
Kavanagh and his colleagues are currently compiling a large-scale registry of patients who are undergoing radiosurgery. Over the next two to three years, they are partnering with the American Association of Neurological Surgeons to collect information on over 27,000 patients who were treated with radiosurgery for benign and malignant brain tumors, in order to identify quality metrics and determine the best ways to select patients for treatment and get the best outcomes.
 
“There are many questions you can think to ask about how something can be done better,” says Kavanagh. “The problem is that there are simply not enough resources or the time available to test every single good question in a classic, randomized, controlled clinical trial.”