December 2016 marked the beginning of a new era of radiation therapy at South Texas Veterans Health Care System (STVHCS), which began treating patients with its new Elekta radiation therapy system (Versa HD). The linear accelerator – which replaced two aging radiotherapy systems and recently completed its second full year of service – has markedly improved treatment speed and accuracy, according to William E. Jones, III, MD, Chief of Radiation Oncology at STVHCS.
“One of the most significant advantages of the new system over the two previous systems is the integrated cone beam CT [CBCT] imaging technology,” he notes. “With the patient on the table, we can do a ‘mini-CT’ right then and there, which enables us to see if the organs have moved since planning. For example, the bowel contents of a prostate cancer patient may have caused the prostate to shift forward. Being able to see the target every day and correct for this motion is a huge change for us.
“We’re delivering with more confidence and greater precision using CBCT,” he adds. “So, we have gradually progressed to using smaller treatment margins around the tumor. That means a minimal amount of healthy tissue surrounding the tumor is exposed to the treatment radiation.”
STVHCS’s lung cancer patients have also benefited from the new system’s imaging capabilities, specifically, the new system’s 4D image guidance technology, which enables clear visualization of moving targets.
“Some patients have lung tumors that can move substantially during breathing,” Dr. Jones notes. “CBCT works well for stationary targets, but moving objects become blurred. By taking a 4D planning scan – which shows the ‘envelope’ of space within which the tumor is moving during the patient’s breathing cycle – we can more easily localize moving tumors.”
STVHC’s Versa HD also features a highly advanced beam shaping device that conforms the radiation beams precisely to the tumor’s shape and ensures that radiation transmission is kept to the absolute minimum.
“Having low transmission means patients are exposed to much lower radiation,” he says.
During the last two years, the radiation oncology department has been able to treat significantly more patients per day, by virtue of the new system’s speed, according to Dr. Jones.
“I don’t think we had ever managed to treat 30 patients in a day with our previous linacs,” he notes. “Even with daily CBCT with the new linac, we’re routinely treating over 30 patients a day. And, we now give prostate cancer patients hypofractionated therapy – 20 fractions versus the typical 39 fractions – which is another operational efficiency we’ve realized. But more importantly, it’s a major benefit for patients who will need to visit the hospital fewer times, some from long distances.”
Additional improvements are on the horizon at STVHCS, as the center gears up to perform Stereotactic Body Radiation Therapy (SBRT) this year. SBRT – a form of radiotherapy that localizes body tumors using their precise 3D coordinates – involves the delivery of a single high dose radiation treatment or a few radiation treatments over time.