A Medical Device Daily

Super-intense radiation delivered by a robotic arm eradicated lung tumors in some human patients just three to four months after treatment, according to a report by medical physicist Cihat Ozhasoglu, PhD, of the University of Pittsburgh Medical Center , presented at this week's 48th annual meeting of the American Association of Physicists in Medicine (AAPM; College Park, Maryland) in Orlando, Florida, concluded yesterday.

Ozhasoglu acknowledged that it is still too early to determine the long-term effectiveness of the treatment, but he and his colleagues said they believe there is promise in this new approach to treating lung cancer and other tumors that are difficult to treat because of breathing movement.

The team's conclusions were reported in a paper titled “Synchrony — Real-Time Respiratory Compensation system for the CyberKnife.”

AAPM said that Ozhasoglu and about 30 of his colleagues form one of the largest U.S. teams devoted to the CyberKnife, a radiation delivery system made by Accuray (Sunnyvale, California) that features use of a robotic arm to aim highly focused X-ray beams at the site of a tumor.

To track the moving tumor, the CyberKnife takes real-time X-ray pictures of the patient while using external markers attached to the patient's chest or abdomen to follow tumors in real time with a few millimeters of accuracy. The researchers also applied Synchrony to treating tumors in the thorax and abdomen, which can move as much as 4 cm during respiration.

The Pittsburgh researchers recently upgraded their CyberKnife by adding a system called Synchrony, which accurately targets tumors that move as a result of breathing. Synchrony instructs the robotic arm to move the radiation source (a linear accelerator that produces X-rays) in sync with the tumor motion.

As a result of the real-time tumor tracking capabilities of the upgraded system, the researchers established detailed methods to treat the tumors safely, otherwise not possible due to lack of sufficient real-time tracking accuracy in conventional radiation machines.

Treating lung tumors with the enhanced Cyberknife requires only one to three sessions lasting 60-90 minutes. In conventional radiotherapy, patients typically get dozens of radiation treatments, each lasting about 15 minutes but requiring 20-30 hospital visits.

In a single treatment, Cyberknife blasts a lung tumor from all sides typically by delivering 100 to150 intense, focused X-ray beams, causing the tumor to absorb roughly 10 times more radiation than in a conventional radiotherapy session.

Cyberknife can deliver so much more radiation because the robotic arm aims the X-rays precisely enough to avoid surrounding healthy tissue.

Main components of the CyberKnife with Synchrony are: Linear Accelerator (LINAC) mounted on robotic arm; two flat panel cameras positioned perpendicular to diagnostic X-ray sources mounted to ceiling; Synchrony-tracking vest with LED markers attached; Camera array which holds three CCD cameras; Synchrony and Target Locating Computers.

Currently there are 76 active CyberKnife sites worldwide (with 45 in the U.S.), and an additional 62 scheduled to be installed globally.

In other product reports from the AAPM meeting:

• IsoRay (Richland, Washington) said its new medical isotope, Cesium 131, is providing another treatment option for prostate cancer patients nationwide. Offering “significant advantages” over other medical isotopes now in use, Cesium-131 represents the “first major leap in seed brachytherapy in 20 years,” IsoRay said.

“Brachytherapy has proven to be effective, but the introduction of Cesium-131 takes this treatment option to a new level. Attendees at AAPM will be introduced to a breakthrough option for fast and effective treatment of prostate cancer,” said Roger Girard, CEO and chairman of IsoRay.

Seed brachytherapy – a procedure in which radioactive seeds are implanted in and around a cancerous tumor — is a proven treatment for prostate cancer, with 50,000 to 60,000 procedures conducted each year. And IsoRay said that clinical data shows that patient outcomes for seed brachytherapy are superior to those for radical prostatectomy, external beam radiation, IMRT, cryotherapy and experimental procedures, at far less cost and higher quality of life.

Available in over 50 locations across the U.S., Cesium-131 delivers its therapeutic radiation faster than other isotope seeds – Palladium-103 and Iodine-125 – and at a reduced risk to patients when compared to surgery and other treatment options, according to IsoRay. Cesium-131 received FDA 510(k) clearance in March 2003.

Due to its unique characteristics, Cesium-131 patients receive a higher initial dosage of radiation that kills cancer cells more quickly, IsoRay said. Its short half-life means that radiation leaves the body sooner than other isotope options.

“Initial research indicates that patients who select Cesium-131 typically experience a shorter duration of normal side effects when compared with other isotope seeds,” said Dr. Steven M. Kurtsman, medical advisor for IsoRay.

• Xoft (Freemont, California), developer of the Axxent Electronic Brachytherapy System, highlighted six studies demonstrating the ability of its Electronic Brachytherapy system to accurately and consistently deliver the therapeutic dose as predicted though treatment planning.

“Electronic Brachytherapy represents a dramatically new way to deliver radiation therapy, which is why educational events such as the Xoft Symposium are crucial to help radiation oncology professionals familiarize themselves with its advantages and what they need to integrate it into their treatment armamentarium,” said Mark Rivard, PhD, associate professor and chief medical physicist at the Department of Radiation Oncology, Tufts-New England Medical Center (Boston).

Xoft also hosted a technology symposium in conjunction with the AAPM meeting. Titled “Using Xoft's Axxent Electronic Brachytherapy System in the Clinic,” a panel of medical physicists focusing on how to incorporate the technology into routine clinical practice for the treatment of breast cancer.

Since receiving FDA clearance for the Axxent System, Xoft said it has worked with radiation oncologists, physicists, and breast surgeons at nine clinical sites to continue physics quality assurance measurements, product refinements and validation.

• Varian Medical Systems (Palo Alto, California), a developer of cancer therapy technologies, exhibited its Eclipse radiotherapy treatment planning system.

Eclipse is capable of producing plans for conventional radiotherapy, intensity-modulated radiotherapy, image-guided radiotherapy (IGRT), brachytherapy, and proton radiotherapy, the company said.

AAPM is a professional organization of more than 6,000 medical physicists.