Mar 23, 2009
Tami Freeman is Editor of medicalphysicsweb.

The emergence of lower-cost proton-therapy systems based on compact accelerators will enable many more patients to benefit from this highly conformal cancer treatment. To this end, several commercial firms are developing compact systems based on a range of technology approaches. One such company is ProTom International (Flower Mound, TX), which teamed up with MIT's Bates Linear Accelerator Center (Middleton, MA) last summer to validate its compact proton-therapy system. Now, the partners have announced successful beam acceleration and extraction from the ProTom system.

The ProTom synchrotron arrived at MIT-Bates earlier this year for validation testing of the accelerator and its subsystems. Following just two months of installation and commissioning, a proton beam was extracted with a beam energy ranging from 30 to 250 MeV. The research team also demonstrated dynamic real-time modulation of the beam intensity within each extraction cycle.

"These tests, overseen by MIT engineers and scientists, represent the first successful demonstration of a proton beam of clinical range from a small-footprint system that will be commercially available in the United States," said ProTom's CEO Stephen Spotts. "We now look forward to completing the formal FDA [Food and Drug Administration] review process in order to make this important new treatment tool clinically available to cancer patients in the US."

Design breakthrough
The proton-therapy system is based on next-generation synchrotron technology originating at the Lebedev Physics Institute in Russia, and to which ProTom has secured exclusive US commercialization rights. The synchrotron has an external-ring diameter of around 16 feet (4.9 m) and a weight of approximately 15 tons. A range of technical advances facilitate proton-beam scanning with a variable pencil-beam size.

"What's been achieved with our device should be considered as a design breakthrough," explained ProTom director Andrew Cowen. "It's a conventional synchrotron, but with many enhancements and improvements - for example, in terms of magnet design, ring construction and the extraction process - that enable us to significantly scale down the size and dramatically reduce the number of components. It's certainly a compact and streamlined system, but it's in a very different category relative to the devices being developed by Still River Systems and TomoTherapy, which I would characterize as more in the area of technology breakthrough."

The ProTom system has already demonstrated pulse-to-pulse energy variability. It also has the capability to perform dynamic energy modulation during a pulse. "At this point, I believe our system is the only one specifically designed for, and capable of achieving, proton-beam scanning with dynamic energy and intensity modulation in three dimensions," Cowen told medicalphysicsweb.

The MIT-Bates researchers will continue to work with ProTom to provide independent validation of the system and help identify further potential enhancements. They are also helping ProTom generate data for the FDA 510k approval necessary to begin treating patients, which Cowen predicts should be in place by the end of this year. In the meantime, the company plans to begin its first round of clinical demonstrations and site visits at the MIT facility in mid-April.

Commercial prospects
The ProTom system, which can serve two treatment rooms from a single synchrotron in a 5000 square-foot facility, was initially designed with smaller hospitals in mind. But Cowen notes that the current economic climate has led many of the larger clinical centres to scale down their plans.

"A number of centres that were looking for four-room solutions just can't get the financing to do that," he said. "As our solution is scalable, they can start with two rooms now, and grow as the patient load increases. And for those hospitals that only need one or two treatment rooms, the price differential is really quite compelling."

Another differentiator is ProTom's business model, in which the company plans to act as a "healthcare services provider". As such, ProTom will not just sell the equipment, but will partner with the host hospital on the design and construction of the proton-therapy facility, and ultimately also in the operation of the centre. "Our clinical and technical resources are considerable," said Cowen, "and something we think our hospital partners will value."

"The exciting point for ProTom is that we've actually got a working machine. We're generating and extracting a proton beam, which I think puts us several steps ahead of other players in the compact system arena," said Cowen. "The market benefits from having competition and alternatives; but now we can demonstrate our capabilities, it's a big step for us and for the field."