Brachytherapy, while receiving increasing use and proof of clinical benefit, requires the deployment of radiation via ionizing radioisotopes and a relatively large infrastructure to handle the radioisotope used and the extensive shielding required by this type of radiation.
But now, an enticing alternative is set to appear over the scientific and commercial horizon, according to Xoft (Fremont, California).
Xoft is seeking 510(k) clearance for its Electronic Brachy-therapy system, dubbed Axxent, a technology that delivers what the company calls “localized, non-radioactive radiation treatment” to a cancer site via highly targeted X-ray.
“Unlike brachytherapy sources containing radionuclides, the non-radioactive Electronic Brachytherapy source can be turned on and off at will, and may be operated at variable voltage to change the penetration properties,” says Mark Rivard, PhD, associate professor and chief medical physicist in the department of radiation oncology at Tufts-New England Medical Center (Boston).
Rivard last week was one of three researchers presenting papers on Xoft’s Axxent brachytherapy alternative at the 26th meeting of the American Brachytherapy Society (Reston, Virginia) in San Francisco, his work focusing primarily on establishing exact dosing parameters for the system.
Altogether, the research papers serve to support Xoft’s contention that Axxent electronic brachytherapy is equivalent to traditional brachytherapy but can be delivered to a larger population of cancer sufferers via greater treatment flexibility and much-reduced infrastructure. The latter feature, especially, makes it deployable at a much wider range of locations, from high- to low-tech, Xoft says.
Rivard told Medical Device Daily that in contrast to the sophisticated radioisotope materials handling – necessitated by radioactive decay, nuclear waste handling, and concerns about its ionizing effects on the body – Axxent requires only “pushing a button on and off, like flicking a light switch. It’s that easy to control.”
Besides featuring greater control of planning and energy delivery, Axxent can be deployed, Rivard says, without the need for heavy shielding to protect clinicians.
According to Marga Ortigas-Wedekind, vice president of marketing and development for Xoft, Axxent is a method for delivering electronic/X-ray radiation “to a tumor bed, or to the tumor directly . . . and we can deposit that radiation very quickly, at a high dose rate,” thus minimizing the effects of X-ray.
She acknowledges its similarity to Mammosite, the system developed by Proxima Therapeutics (Alpharetta, Georgia) – but not using Mammosite’s radioactivity – and one of the predicate devices in Xoft’s 510(k) application for adjunctive treatment of breast tumors after resection.
Following resection, a balloon applicator – “like a large version of an angioplasty balloon,” Ortigas-Wedekind says – is placed in the cavity. “Delivery of the radiation is made through a central lumen to the distal end, controlled by our controller, and then essentially you turn the machine on and deliver a set program of radiation.”
Treatment is delivered over a five-day period, twice a day, “on average,” she says, at 15-minute intervals, vs. seven weeks for external beam radiation.
The company has not carried out human efficacy studies, Ortigas-Wedekind acknowledges, but is supporting its application for clearance with a variety of analogies to standard brachytherapy and other brachytherapy devices (see sidebar, page 5).
She says that Axxent has increasing potential in a diagnostic environment in which smaller breast tumors may be found earlier and, after resection, have clear margins and no metastases.
Importantly, she points to the benefits of greatly reduced treatment times and deployability at almost any health facility. Both, she emphasizes, may push forward the increased treatment via an accelerated partial breast irradiation protocol, increasingly recommended as an alternative to mastectomy.
The logistical benefit is key, Ortigas-Wedekind notes, considering the complications of treatment for women who are distant from a treatment center and have responsibility-crowded lives. Here, she cites studies showing “an inverse relationship between distance to a clinic and willingness to undergo treatment.”
She declines predicting a timeline for U.S. clearance of Axxent, noting that “it’s never good to second-guess the FDA,” but points to commercialization gear-up by Xoft.
Assuming device approval, the company will move to human studies and then commercialization of Axxent in conjunction with a five-year device registry.
As to Xoft’s history, Ortigas-Wedekind says the company first targeted “a vascular play.” But with the emergence of drug-eluting stents it redirected its focus to oncology.
This redirection was highlighted by A, B and C rounds of financing, the most recent coming last month with $30 million in funding for the push to commercialization (MDD, May 9, 2005).
As a follow-on to the breast cancer application, the company “is working on prototypes which will deliver a radiation source for endometrial cancer,” Ortigas-Wedekind says.
Besides Rivard’s paper delivered at the brachytherapy meeting, other papers were presented by Steve Axelrod, principal scientist at Xoft, analyzing the use of radiochromic film to evaluate delivery of prescribed doses in clinical applications simulated using a water phantom. This study confirmed that the X-ray source parameters described by Rivard accurately represented the radiation dose distribution.
The third study, led by John Rieke, MD, radiation oncologist at the Puget Sound Health Care System (Puget Sound, Washington), validated the performance of the Axxent system including the safe delivery of 10 fractions in a five-day period in animals.
Overall, Xoft believes that, with Electronic Brachytherapy, “tens of thousands of patients will have greater access to therapy that is delivered more easily and conveniently.”