Wireless 'beacons' promise means to track shifting cancer tumors

August 20, 2003

Markers would be implanted prior to radiotherapyThe frontlines in the battle against cancer in the body are the boundaries between healthy and malignant tissue. Unintentional damage to normal tissue must be minimized, but in this

Markers would be implanted prior to radiotherapy

The frontlines in the battle against cancer in the body are the boundaries between healthy and malignant tissue. Unintentional damage to normal tissue must be minimized, but in this struggle the patient can be the oncologist's worst enemy. Changes in body shape over a series of treatments or patient movement during a session-even the normal process of breathing, especially when a lung tumor is being irradiated-can cause the beam to go beyond the target. Calypso Medical Technologies is developing an answer.

The Seattle start-up is building markers, called Beacon Transponders, designed for implantation in tumors. These transponders would relay information indicating the position of the tumor in 3D space. Theoretically, the tumor would then be mapped into a radiotherapy system, for example, that could be programmed to adjust the aim of the beam according to shifts in the tumor position.

Technical studies presented at the American Association of Physicists in Medicine (AAPM) annual meeting in San Diego Aug. 10 to 14 attested to the theory of operation behind the technology. They demonstrated with phantoms that the transponders can be used to locate and continuously track moving targets with submillimeter accuracy.

"The goal is to provide the information that oncologists need so they can treat what they intend to treat," said Eric Meier, president and CEO of Calypso Medical.

It sounds like a relatively simple concept, but its implementation is anything but. Tumors can shift markedly between treatments due to changes in the body. Shifts occur moment to moment as well, due to normal physiologic events, such as organs filling and emptying, or from respiration.

"Clinicians' ability to plan pinpoint therapy far exceeds their ability to deliver the level of precision therapy they desire because of moving treatment targets," said John Wong, Ph.D., director of clinical physics at William Beaumont Hospital in Royal Oak, MI.

Wong presented at the AAPM meeting on the theory behind Calypso's electromagnetic tracking system. Technologies such as Calypso's promise to narrow the gap in precision between planning and implementation. The beacons' positions would be captured as part of the imaging workup of the patient, Meier said. These positions would be loaded into the treatment plan as part of the process to determine the isocenter of treatment. This information would then be transferred to the Calypso system, which would provide coordinates indicating the location of the tumor.

Clinical tests are scheduled to begin soon. If they demonstrate that the system can be used to track tumors in real-time, the technology might be integrated into radiotherapy equipment to provide assistance in aligning the radiation beam.

"We would be generating objective information," Meier said. "This would make the therapist's job easier and improve efficiency."

Meier was sensitized to the challenges of radiation oncology while an executive at Johnson & Johnson. He founded Calypso Medical Technologies four years ago in response to what he perceived as one of the most serious problems, moving targets being addressed by stationary radiation sources. Meier found the solution in military technology and, with a cadre of engineers, evolved the technology to its current form.

"Starting with the problem allowed us to take a blue-sky approach, settling on the concept of a smart marker, or 'beacon transponder,' as the best way go after it," he said.

The company has raised $37 million in two rounds of venture capital funding. Meier anticipates the need to raise more money in the future to scale up the business, but he has not set a specific time. The most immediate concerns are nailing down the regulatory requirements to obtain FDA approval and conducting the clinical tests necessary to pass the regulatory review. Sales and marketing approaches are in the early stages of development.