A few short months after the Radiochirurgia Zagreb (Ray of Hope) Cancer Center in Croatia opened in December of 2016, the center launched its SRS/SBRT program, making it the first treatment center in the country to offer these treatments, according to Professor Dragan Schwarz, MD, the abdominal surgeon and former Croatian State Secretary in the Ministry of Science who serves as head of this unique private clinic. To date, clinicians at the clinic have treated some 600 patients; 500 of them received radiosurgery.
Ray of Hope utilizes a multidisciplinary treatment approach, with cases reviewed by a team that includes a surgeon, radiation oncologist, radiologist, and physicist, who work together to develop each patient-specific treatment protocol. Treatments are delivered using the Edge™ radiosurgery system.
“SBRT in our country and region began with the arrival of the Varian Edge system in our clinic,” said Professor Schwarz. “We chose to launch our program with the Edge system because it allows us to perform both radiotherapy and radiosurgery treatments, and to deliver SRS/SBRT treatments of the highest quality. We also appreciate the fact that, for many treatment sites, we don't need implanted fiducial tracking; we can rely on the system's optical guidance technology.”
Prof. Schwarz characterized the process of acquiring, installing, and commissioning the Edge system and training new medical personnel as having gone smoothly. Installation took about two months, and commissioning another month, he said. During that time the staff underwent both formal and informal training. They observed processes at several European SRS/SBRT centers. And they attended Varian classroom training, including a course on advanced physics techniques for VMAT/IMRT and an Advanced Techniques Clinical School for SRT.
“Members of our team have at least 10 years of experience in a clinical radiation therapy setting, so, while the learning curve is steep, we got our SRS/SBRT program running one month after our first radiotherapy treatment,“ Prof. Schwarz said.
SBRT for Lung, Liver, and Pancreatic Cancer
SBRT patients are treated with single or multiple fractions, depending on their diagnoses. According to radiation oncologist Hrvoje Kaučić, the team favors hypofractionated treatments including, when possible, treatments completed in a single session as long as an ablative dose can be administered.
“We treat 70% of our SBRT patients in a single fraction,” he said. “Select patients who are able to hold their breath are treated using a deep inspiration breath hold (DIBH) technique whenever possible, however, every patient is monitored either with the OSMS or Calypso® extracranial tracking, even if no gating is planned. This ensures that there are no patient movements that would compromise the treatment. We use cone-beam CT imaging for final patient positioning prior to every fraction.
For example, a typical lung metastasis case--outside the so-called ‘no-fly zone’--consists of one fraction of 31.25 Gy (25 Gy to 80% isodose line); 99.5% of PTV volume receives at least 25 Gy, and one isocenter (plan) per target using a CBCT and kV imaging set up and OSMS gating in DIBH,” Dr. Kaučić described. “There is no immobilization. Inside the so-called ‘no-fly zone,’ we use a fractionated regime—three to five fractions.”
The center's approach to treating pancreatic cancer involves the use of gating that is based on Calypso internal tracking. Prof. Schwarz discussed a patient who had been diagnosed with a locally advanced ductal adenocarcinoma of the pancreatic head, with infiltration of the superior mesenteric artery.
“We chose an SBRT approach, using five fractions of 9 Gy with a 2-millimeter margin around the planning target volume,” he said. Three Calypso beacons had been percutaneously implanted under ultrasound navigation. The treatment involved a combination of deep-inspiration breath-hold and gating based on the movement of the beacons.
Two months after treatment, Dr. Kaučić said, the lesion was discretely smaller, and there were no new distant lesions. Four months after treatment, the size of the treated lesion had been reduced significantly, and there were still no new distant lesions. To date, the patient has reported no significant toxicities.
Motion tracking is accomplished using the OSMS for frameless intracranial SRS.
“For our SRS patients, we are often dealing with metastatic disease, meningiomas, and salvage by irradiation of glial tumors,” said Prof. Schwarz. “We treat metastases in a single fraction whenever feasible; the dose depends on the size of the metastases. Typically, we apply 25 Gy to the prescribing isodose line. For meningiomas up to 5 centimeters, we use a typical dose of 14 Gy. Multiple metastases are treated with a single isocenter,” Prof. Schwarz explained. “Typical treatment time is less than 30 minutes.”
The Ray of Hope team uses Varian’s EclipseTM software for planning their SRS/SBRT treatments. According to Prof. Schwarz, the planning process is similar to standard radiotherapy planning except that physicists determine the CTV to PTV margin on a patient-by-patient basis, and more care is taken to assure that the machine's mechanical parameters can deliver the plan with sufficient quality. All treatment plans have to pass a gamma criteria of 3% / 1mm before the patient is treated. The team uses the Radiation Therapy Oncology Group (Timmerman) criteria for specifying doses to organs at risk.
Another benefit of LINAC-based SRS and SBRT are shorter treatment times. Most SRS/SBRT treatments fit into a half-hour time slot, Prof. Schwarz noted, except for DIBH treatments, which take about an hour per isocenter.
“Patients enjoy their short treatment times as compared to treatment with the Cyberknife or Gamma Knife. That multiple targets can be treated on a single isocenter, combined with the ability to use a high dose rate, means that patients are often treated in a quarter of the time—or even less—than with the Cyberknife or Gamma Knife,” Prof. Schwarz said. “Also, real-time motion tracking is accomplished without any additional dose of ionizing radiation.”
The information captured herein represents the genuine experience of the attributed individuals and may not necessarily represent the views of Varian or the above referenced institution. Individuals were not compensated for their testimonials. Radiation treatment may not be appropriate for all cancers. Individual results may vary.