Proton Therapy

PROTONS ARE AN example of particle radiotherapy and are produced by a cyclotron or synchrotron. Proton beam therapy has become of interest because of its ability to accurately target and kill tumors that are either near the surface or deep seated within the body. Unlike more conventional radiotherapy treatment techniques, which employ the use external beams of electrons or X-rays, proton beam therapy offers the potential for providing an improved distribution of radiation dose such that normal, healthy tissue surrounding a tumor is spared, thereby reducing collateral side effects from radiotherapy.

Protons were first proposed to have a role in the treatment of human malignancies in 1946 by Robert [Page 706]Rathbun Wilson, Ph.D., while working at the Harvard cyclotron laboratory. Soon after, the use of proton beam radiotherapy for cancer treatment was pursued at select centers in the United States, Russia, and Sweden.

The first treatments were for patients with pituitary disorders and were performed in the mid-1950s by a cyclotron built for physics research at the Berkeley Radiation laboratory. The use of protons to treat the pituitary was of particular interest because the well-defined beam of a proton made it possible to deliver a large dose to the pituitary without causing excessive damage to nearby structures in the central nervous system.

After the initial success of this treatment, similar endeavors were undertaken at the Massachusetts General Hospital by a neurosurgeon by the name of Dr. Ray Kjellberg in the 1960s. Dr. Kjellberg began treating small intracranial targets with radiosurgical techniques at the Harvard cyclotron laboratory. Together with the physics group at the Harvard cyclotron laboratory, Dr. Kjellberg was able to develop instrumentation, methodology, and techniques for radiosurgical beam delivery, using protons. The treatments by Kjellberg have evolved into an active proton therapy program at the Massachusetts General Hospital, now known as the Northeast Proton Therapy Center, which is still active today.

In the 1960s and 1970s, while work continued at Harvard and Berkeley cyclotron facilities, further research in proton therapy was undertaken at several different physics research facilities around the world, most notably in Russia. Most of the work in Russia was done at the Joint Institute Nuclear Research and the Moscow Institute for Theoretical and Experimental Physics and in St. Petersburg. Soon after, treatment with proton beams was also begun at the National Institute for Radiobiological Sciences in Chiba, Japan, which is where a spot-scanning system for proton therapy was first developed.

The work from such institutions and others around the world has laid the foundation for proton radiation treatment as it is delivered today at active hospital centers. The first hospital-based proton therapy program in the United States was built in Loma Linda, California, in the 1980s. The first patient was treated at the Loma Linda Medical Center in October 1990. Since the inception of the center, nearly 12,000 patients have been treated at the Loma Linda cancer center. Worldwide, almost 45,000 patients have been treated with proton beam radiotherapy since its first use at the Berkeley Radiation laboratory.

Today, there are six active proton therapy centers across the United States. In addition to the Loma Linda cancer center, proton therapy treatment is carried out at the Northeast Proton Therapy Center at Massachusetts General Hospital, which was recently renamed the Francis H. Burr Proton Therapy Center. Treatment is also available in Sacramento at the University of California, Davis, Proton Facility, a facility that is dedicated to proton therapy for ocular tumors, and at the Midwest Proton Radiotherapy Institute at Indiana University. Most recently, two new proton treatment facilities were started in Houston, Texas, at the University of Texas M.D. Anderson Cancer and at the University of Florida Proton Therapy Institute in Jacksonville, Florida.

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