Wednesday, July 29, 2015

Treating Previously Untreatable Cases with Proton Beam Radiosurgery


At the Francis H. Burr Proton Therapy Center at Mass General Hospital, Neurosurgical Director Dr. Paul Chapman collaborates with colleagues in the Department of Radiation Oncology to treat neurosurgical patients with Proton Beam Radiosurgery.  Presently, Mass General is the only medical facility in the world to offer radiosurgical treatments utilizing proton radiation.

Radiosurgery delivers an intense beam of radiation to tumors and vascular abnormalities deep within the brain. Proton Beam Radiosurgery takes advantage of the unique physical properties of proton radiation to deposit the radiation energy very precisely within the target. Protons are charged particles that travel through tissue without giving up significant amounts of radiation until they reach their final depth of penetration, where a burst of high dose radiation is given off within the tumor or vascular malformation being treated. This precisely-directed burst of radiation is known as the Bragg Peak. Beyond that point there is no further radiation because the protons have been absorbed by the tissue. This results in less radiation to normal tissues, in contrast to other types radiation such as gamma rays and x-rays. This is a significant advantage when treating lesions located in critical areas of the brain. For younger patients and children, this also minimizes the potential long-term effects of radiation on normal tissues.

The Development and Evolution of Proton Beam Radiosurgery
Proton Beam Radiosurgery has a long history at Mass General. Taking advantage of the existing Cyclotron Laboratory at Harvard University in Cambridge, Mass General neurosurgeons, under the direction of Dr. William Sweet and Dr. Raymond Kjellberg, spurred the development of technology necessary to adapt proton radiation to the care of Mass General patients. The first patient treated was a three year old with a malignant brain tumor in 1962.  The outcome was successful.  Dr. Kjellberg continued to care for patients there until 1992, ultimately treating over 3000 tumors and vascular malformations with proton beam radiosurgery. During 1989-1992, a new treatment system was designed and implemented, incorporating the latest technical advances in medicine and physics. This new stereotactic alignment system for proton radiosurgery (STAR) continues in use at the Mass General’s Burr Proton Therapy Center today.
Dr. Chapman, who has been practicing at Mass General for 50 years, was Chief of Pediatric Neurosurgery from 1972 until 2000. In 1989 he undertook major responsibility for the redesign and installation of the modern STAR radiosurgical system at the Harvard Cyclotron Laboratory.  In collaboration with the Mass General Department of Radiation Oncology, he began treating patients there in 1991. The STAR proton radiosurgery program expanded rapidly during the 1990’s and was ultimately transferred to the recently opened Francis Burr Proton Center on the campus of Mass General in 2002. Since 1991, Dr. Chapman has served as the Neurosurgical Director of the Proton Beam Radiosurgery Program.

The Clinical Importance of Proton Beam Radiosurgery
For children, Proton Beam Radiosurgery is particularly advantageous due to their immature brains and other tissues in the head. With the ability to optimally confine high dose radiation specifically to the targeted abnormality such as a tumor, one can lessen the long-term effects of radiation on a normal brain. “It is so gratifying to effectively treat otherwise inoperable conditions or those for which the risk of surgery is excessive,” says Dr. Chapman.  Approximately 80 percent of the treatments performed are for tumors, either benign or malignant, while the other 20 percent consist of vascular malformations, especially arteriovenous malformations (AVM).

Proton Beam Radiosurgery Creates New Hope for Patients
In the case of most benign tumors such as meningiomas, acoustic neuromas and pituitary adenomas, the rate of success is generally excellent, compared to more invasive neurosurgical procedures. In the case of malignancies such as brain metastasis, the treatment provides similar benefits for patients who require a simple, non-invasive means of palliating their illness. The treatment for AVM’s is similarly successful.  One woman in her early 20’s had an inoperable malformation deep in the center of the brain, which had hemorrhaged massively at least six times within a several year period.  “On each occasion she would slowly recover and wait anxiously for the next catastrophe that might take her life or leave her disabled. The new STAR system had only recently become available, prior to which her treatment would have been problematic at best,” says Dr. Chapman. Her treatment eliminated the AVM and has allowed her to lead a healthy, gratifying life in the following 20 years.

Collaboration Brings Continuing Advances in Proton Beam Radiosurgery
Through close, multidisciplinary collaboration with Mass General colleagues, the Mass General Neurosurgical Proton Beam Radiosurgery Program continues to advance successful treatments for patients with previously untreatable conditions.  An area of major interest is the treatment of giant brain AVMs which are at present problematic for treatment by any means, including radiosurgery.

 “All Proton Beam Radiosurgery is a collaborative effort with our Radiation Oncology Department,” says Dr. Chapman. “As Chief of the Neurosurgery Radiosurgery Program, I work closely with Dr. Jay Loeffler, Chairman of Radiation Oncology and
Chief of the Radiation Oncology Radiosurgery Program at MassGeneral.” 

Dr. Chapman also works with Dr. Daniel Cahill, III, MD, PhD, within the Neurosurgery Department. Dr. Cahill is a Mass General Neurosurgeon who has extensive experience in treating brain tumors and malignancies with radiosurgery, including the proton beam.
Mass General is currently expanding its Proton Beam facilities on campus in order to treat more patients and a wider range of conditions. Dr. Chapman is hopeful he and his colleagues can continue to make significant progress, positively impacting patient outcomes for even the most critical cases.

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