Using Technology to Administer Radiation

MAY 01, 2009
Christina T. Loguidice
In the well-attended session, "Bench to Bedside—It's Not All Magic: How Technology in Radiation Has Changed Care," Marilyn Haas, PhD, RN, Mountain Radiation Oncology, Asheville, North Carolina, and Stephen Hahn, MD, University of Pennsylvania, Philadelpia, introduced the audience to several relatively new types of sophisticated machinery that allow radiation to be distributed more accurately, resulting in less toxicity to surrounding tissue. The two main systems discussed were proton beam therapy and the Cyberknife system. The authors had no conflicts of interest to disclose.

Proton beam therapy
Proton beam therapy is an external beam radiotherapy in which protons are accelerated in a particle accelerator to almost the speed of light and then slowed down to the target speed before hitting the tissue. Protons remain concentrated and do not scatter much; thus, this modality results in 70% less radiation being delivered to the surrounding healthy tissue when compared with normal radiation therapy. Basically, the radiation conforms to the shape of the patient's tumor.

Dr. Hahn indicated that proton beam therapy may be especially useful in pediatric patients, who are especially sensitive to radiation. The problem with this therapy is that it is incredibly expensive, having a start-up fee of $125 million. As a result, this treatment costs four times as much to administer than more conventional radiation therapies, and it may not be covered by most insurance providers. It also requires a tremendous amount of space—over 92,000 square feet. Currently, only 5 centers in the United States offer this therapy. For this reason, patients receiving treatment are prioritized, and those with low-risk cancers are often placed on long waiting lists.

Another advantage of this proton beam therapy is that it allows chemotherapy agents to be used that could not be administered before in the setting of radiation therapy, which offers new treatment options to certain patients, potentially improving their suvival. However, Hahn cautioned that although toxicities appear to be lower, this findings and improved survival need to be confirmed through randomized trials.

The Cyberknife
The Cyberknife is a frameless robotic system that generates radiation from a small particle accelerator and delivers the radiation from a robotic arm that moves around the patient, allowing the radiation to be administered from various angles. This allows more precise tissue targeting and less radiation from damaging normal tissue. This form of radiation can treat both intracranial and extracranial tumors, and the system works in real-time. Another advantage is that no patient tattoos are required.

Some of the drawbacks are its expense, and, in cases where fiducials are used, such as for soft tissue tumors, patients need to recover from any swelling before treatment can be administered. There also may be some risk for infection. These factors contribute to the time-consuming process of administering this treatment. Patients also may be nervous having a rotating arm moving within inches of their body, and sometimes sedation may be required. Nevertheless, the system does offer an alternative to traditional treatment and reduces the risk for toxicities.

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