Studies Show that RapidArc Radiosurgery is a Viable, Time Efficient Way to Treat Multiple Brain Metastases

Treating multiple brain metastases with single isocenter RapidArc® radiosurgery—a technique for treating several tumors at once rather than one at a time—can deliver results that are equal or comparable to other types of radiosurgery, according to research teams from the University of California, San Diego (UCSD), the University of Birmingham, Alabama (UAB), and other institutions. RapidArc Radiosurgery, which is a term for volumetric modulated arc radiosurgery delivered using a medical linear accelerator (linac) from Varian Medical Systems

, can also be completed in substantially less time, researchers report. One reason for the speed are the properties of the Varian beam-shaping device, called a multileaf collimator, which features 120 narrow slats that can slide in and out and past each other to produce multiple apertures of virtually any shape, making it possible to target more than one tumor at a time during a treatment. Cone-based and cobalt-based systems like Cyberknife® and Gamma Knife® are generally limited to targeting one tumor at a time. In a single-center, retrospective review of 15 patients with multiple brain metastases who were treated with RapidArc radiosurgery between 2009 and 2011, researchers from UCSD noted local tumor control and overall survival rates that were equal or comparable to conventional radiosurgery approaches. The study, published online prior to print in Neurosurgery, reports that no toxicity above grade 2 was observed.1 "Our clinical experience with Rapid Arc Radiosurgery is that it reduced treatment time while accurately conforming the radiation plan to the intended targets," said Clark C. Chen, MD, PhD, chief of stereotactic radiosurgery and vice-chairman of academic affairs, UCSD neurosurgery. "Each treatment of multiple brain metastases in our study was completed in under eight minutes. Reduced treatment time not only optimizes efficiency of institutional work-flow but, more importantly, maximizes patient comfort and the treatment experience." At the annual meeting of the American Association of Neurological Surgeons (AANS) last month, a poster presentation by Evan Thomas, MD, PhD, from the University of Alabama, Birmingham (UAB), reported on a retrospective review of 34 patients with multiple metastases treated with RapidArc Radiosurgery between 2010 and 2014.2 As described in their Neurosurgery article last year, the UAB team follows a particular planning approach for RapidArc treatments that incorporates the use of non-coplanar arcs to maximize the number of treatment angles, along with key optimization criteria that minimize the amount of low dose "spill" reaching normal brain tissues during treatment.3 "Preliminary results indicated that the toxicity profile associated with these treatments is similar to other modalities, including multi-isocenter approaches, such as Gamma Knife and Cyberknife," Thomas said. "We saw no Grade 4 or 5 toxicity. Grade 3 toxicity occurred in one patient. Grade 2 toxicity occurred in eight patients, consisting mainly of headaches that responded well to steroids. In this patient population, the likelihood of toxicity was mainly associated with previous cranial irradiation treatments and the volume of tissue being irradiated." Thomas will take part in two presentations about the UAB approach to RapidArc Radiosurgery at the International Stereotactic Radiosurgery Society (ISRS) Congress in Yokohama, Japan next week.4 One will cover a case study wherein RapidArc Radiosurgery was used on five separate occasions to treat a single patient for multiple brain metastases that recurred (Abstract O-59). The second will demonstrate the feasibility of treating numerous (i.e. 15) brain metastases with RapidArc Radiosurgery using Varian's TrueBeam® STx system (Abstract O-48). "Because such treatments can be delivered very quickly, in less than 20 minutes, and with great accuracy, some may find the technique preferable to whole brain radiotherapy or Gamma Knife radiosurgery," Thomas said. Also at the upcoming ISRS Congress, four other research teams will present abstracts describing work on the use of RapidArc Radiosurgery to create high quality treatment plans for treating targets in the brain: Joe Ho, PhD, and his colleagues at the California Pacific Medical Center in San Francisco, California, will present a practical treatment planning protocol based on the RapidArc technique. The protocol, which is very similar to the UAB model, produces RapidArc Radiosurgery treatment plans that are equal or comparable to Brainlab and Gamma Knife approaches, and much faster to deliver. (Abstract O-55) A poster presentation by Senthilkumar Natarajan, senior medical physicist, plus his colleagues at the Kovai Medical Center and Hospital in Coimbatore, India, will report on how the UAB approach enabled them to produce treatment plans for cranial targets that achieve a 38% reduction in dose to normal brain tissues, a 30% reduction in the Gradient index (which correlates with how much healthy tissue outside the targeted area is impacted), and a 30% increase in conformity. (Abstract P-77) Sabbir Hossain, PhD, assistant professor at the University of Oklahoma Health Sciences Center, will present an abstract comparing RapidArc Radiosurgery plans with Gamma Knife plans for treating three patients with four to six brain metastases each. He and his colleagues found that their approach to RapidArc Radiosurgery enabled the production of quality treatment plans that improved on Gamma Knife plans with respect to specific parameters, including conformity index, integral dose, and dose to normal brain tissues. (Abstract O-56) Yong Cha, MD, PhD, co-director of the Thoracic Oncology and of the Stereotactic Body Radiation Therapy programs at the Norton Cancer Institute in Louisville, Kentucky, will report on the use of RapidArc Radiosurgery to treat ten patients, each with two to eight brain metastases. The Norton team refers to the approach as linac-based single-isocenter cranial radiosurgery (SICR). According to the presentation abstract: "SICR for multiple brain metastases is feasible and demonstrates excellent local control. Given the short treatment time and excellent plan quality, SICR is an excellent treatment option for patients in certain clinical scenarios." (Abstract O-50) "It is very gratifying to see the amount of clinical research focusing on the promise of treating multiple brain metastases with linac-based RapidArc radiosurgery," said Kolleen Kennedy, president of Varian Oncology Systems. "We are excited to see so much early scientific evidence that this approach is a viable option compared to other forms of radiosurgery because it delivers results that are at least equal or comparable, with substantially greater speed, efficiency, and convenience for patients."