|Proton Beam Radiotherapy
written and compiled by doctordee
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|About Proton Beams|
For background information and definitions, this is a short www.cancer.gov paper About Radiotherapy
Proton radiation is a form of external-beam radiation treatment. Radiation oncologists (physicians who specialize in radiation treatments) can treat in two major ways: by implanting radioactive materials in the body [brachytherapy] or by using machines to generate beams that penetrate the body from outside [external beam]. Proton radiation is delivered by the second method. Other forms of external-beam radiation therapy include x-ray therapy and Cobalt-60 gamma-ray therapy. External beam radiation does not remain in the body. Your body does not become radioactive, and there is no risk of radiation exposure to others.
Proton beam therapy is a radiation treatment that delivers high dose radiation to a very localized site. Protons, being particles instead of x-rays, slow down faster than photons. They deposit more energy as they slow down, culminating in a peak (called a Bragg peak). This allows the majority of radiation to be delivered to the target site with less scattering of radiation around and beyond to the adjacent normal tissues.
Proton beams can be conformed [shaped in three dimensions] to fit the target area. The beam can be carefully shaped to the dimensions of the tumor, and so deliver most of the radiation to the targeted tumor mass, not to the surrounding normal tissue. This tissue-sparing is unique to proton beam therapy.
Proton beam radiotherapy contrasts with conventional Xray or Gamma ray radiation therapy [often called PHOTON beam] due to the unique properties of minimal scatter as the proton beams pass through the tissue, and deposit the ionizing energy at a precise depth (the Bragg peak). Thus radiation exposure to surrounding normal tissues is minimized, permitting higher radiation doses to the target area and improved local control, with less damage and side effects.
Protons, which are positively charged subatomic particles, deposit energy differently than x-ray beams do. Compared to an x-ray beam, a proton beam that is delivered with sufficient energy (or "modulated") has a low "entrance dose" (the dose in front of the tumor), a high-dose "Bragg peak" region, which is designed to cover the entire tumor, and no "exit dose" beyond the tumor. In contrast, X-ray beams may deposit most of their dose in tissues in front of the tumor, and continue to sleet through the body after passing through the target area.
As of November 1, 2002, more than 32,000 patients around the world had been treated with proton beam radiotherapy. The effectiveness of proton beams for treating cancer show in almost every tumor site examined. The higher tumor doses and lower normal-tissue exposure have improved local control and reduced acute and late complications as compared with x-ray therapy. [from Loma Linda website information]
|References and URLs|
Current Opinion in Orthopaedics 2002; 13(6):434-439
Proton beam therapy in the management of bone and soft tissue sarcomas
Thomas F. DeLaney, MD
For cancer treatment, protons, the nuclei of hydrogen atoms, can be accelerated to high energies, extracted, and transported to treatment rooms where the proton beam undergoes a series of modifications (spreading, modulation, and shaping) that conform the dose in a particular patient to the tumor target. Because of their charge and mass, there is no dose delivered beyond the desired target. Proton beam therapy thus provides a means to reduce both the volume of irradiated normal tissues and the radiation dose they receive. This may permit higher doses to the tumor and achieve a higher tumor control probability without increasing the frequency or severity of treatment-related morbidity. Additionally, the more conformal treatment volumes of proton therapy should result in a reduced frequency and severity of comorbidity between radiation and chemotherapy, thus allowing for improved tolerance of the patient to therapy, better treatment compliance, and increased treatment intensity.
For more information
Search Pubmed Proton Beam and Sarcoma
Search Pubmed Proton Beam and Cancer
About proton beam
|Where to Go?|
As of November 2003 there are two major hospital-based facilities that treat patients with proton beams on a regular basis: Loma Linda University Medical Center (LLUMC), in southern California and the Northeast Proton Treatment Center, which opened in November 2001 at Massachusetts General Hospital in Boston. Another U.S. facility, the Midwest Proton Radiotherapy Institute will open at Indiana University, soon. The University of Florida at Gainsville and MDA are both planning centers in the future as well.
About Loma Linda
Criteria for treatment
The major problem we have is that Loma Linda and MGH are the only two facilities that will do Proton Beam Therapy on cancer metastases.
Loma Linda will not do Proton Beam Radiotherapy on a patient if there is other extensive disease. As one doctor said to me, "We like to get a bang for our buck." I do not know about Mass General's policies, it has only been in operation a short time. MGH and the midwestern facility are new arrivals on the scene, and their policies about metastases and extent of metastases are currently unknown.
Other places might do primaries. Contact the proton beam centers and ASK. It might be possible to FedEx your scans and receive a preliminary opinion quickly.
Some Proton Therapy Links. There are further facilities worldwide.
Harvard Cyclotron Laboratory
Northeast Proton Therapy Center
Loma Linda University Medical Center, 11234 Anderson Street, Loma Linda, CA 92354.
Tel: 909 558 6000
U of California, Davis
Midwest Proton Radiation Institute
National Association for Proton Therapy
TRIUMF, Canada protons
TRIUMF, Canada pions
CPO, Orsay, France
TERA foundation, Italy
The Svedborg Laboratory, Sweden
ITEP, Moscow, Russia
HIMAC, Chiba, Japan
NAC, South Africa
Proton Beam Radiation at Loma Linda From Dave M
I received Proton Beam Radiation information by calling 1-800-PROTONS. The video and pamphlets were sent from Loma Linda University Medical Center Proton Treatment Center.
Loma Linda Website
If you click on 'Publications' on the left side of the web page, you are taken to "Published Articles" where you can then find "Clinically Related Publications" by the center's faculty, with links to Medline when available.
Before getting into why they say Proton beam radiation may be better than photon (x-ray) radiation, they state that the following sites are presently being treated:
BRAIN AND SPINAL CORD
including isolated brain metastases, pituitary adenomas, and arteriovenous malformations (AVMs).
TUMORS AT THE BASE OF THE SKULL
including meningiomas, acoustic neuromas, chordomas, and chondrosarcomas.
including uveal (choroidal) melanomas and neovascular formations resulting from the "wet" form of macular degeneration.
CANCERS OF THE HEAD AND NECK
including primary and recurrent nasopharyngeal cancers and locally advanced oropharyngeal cancers.
TUMORS OF THE CHEST AND ABDOMEN
including inoperable non-small-cell lung cancer and chordomas and chondrosarcomas of that region (usually abutting the spinal cord).
TUMORS OF THE PELVIS
including prostate cancers, other unresectable pelvic cancers, and chordomas and chondrosarcomas of that region (also below the spinal cord).
including brain and spinal cord tumors, orbital and ocular tumors, sarcomas of the base of the skull and spine, and abdominal and pelvic malignancies such as Wilm's tumor.
Loma Linda's Proton accelerator was built by Fermilab and was the first hospital-based proton center and has been in operation almost 10 years. In Boston, Massachusetts General Hospital, in cooperation with Harvard University, will have the second hospital-based system, to open in 2001. (I am paraphrasing from their pamphlet, I personally know nothing about any of this)
Both the video and pamphlets explain how proton beam radiation is different from x-ray radiation.
Photon radiation (x-ray) is delivered and most of its energy is deposited on the normal tissue on the skins surface, and some also is deposited beyond the targeted tumor which can result in unnecessary damage to healthy tissues.
Protons are energized to specific velocities that determine how deeply in the body the protons will deposit their maximum energy. They state that "proton therapy is a more precise form of conformal radiation, ... that can be shaped very closely to the tumor and allows them to deliver higher doses to the tumor while minimizing damaging side effects."
The positive charged protons pass near the negatively charged electrons, pulling the electrons out of their orbits (ionization), this changes the characteristics of the atom, which in turn changes the characteristics of the molecules of the target. This is the basis for all forms of radiation therapy. Because protons have a heavier mass, and can be energized to a specific velocity, it can be determined how deeply in the body protons will deposit their maximum energy. As the protons move through the body they slow down, causing increased interaction with orbiting electrons until they reach their targeted stopping point.
Because of ionization, the radiation damages the DNA, which in turn destroys specific cell functions, which may include the ability to divide or proliferate. Enzymes attempt to rebuild the injured area of the DNA, but a cancer cell's ability to repair molecular injury is frequently inferior. As a result, cancer cells sustain more permanent damage and subsequent cell death than occurs in the normal cell population. (This is usually applicable to all forms of radiation therapy). [And can result in more de-differentiation of any cancer cells that survive. Ed.]
A proton beam radiation oncologist can increase the dose to a targeted mass, while reducing the dose to surrounding normal tissue.
That's it in a nutshell. The pamphlet is 20 pages and explains much more.
Erin, on the LMS List, researched proton beam therapy, and posted in October 2001:
"Houston's M.D. Anderson Cancer Center is in development and years away."
There is another proton beam therapy unit opening in the Midwest.
Indiana University's Midwest Proton Radiotherapy Institute (MPRI) is the only one of its kind in the Midwest. The new facility will have low cost family living facilities so the patient's family/caregivers can be with them during the timeline of treatment regimen.
Dick, on the LMS List, wrote to MGH in Nov 2001:
There has been some question as to the status of the Massachusetts General Hospital Proton beam facility. I decided the easiest way to find out the "facts" was to write them. The following is their response:
Dear Mr. Whiting,
The NE Proton Therapy Center started treating patients last week and will be treating patients on an ongoing basis. We will be accepting patients for new protocols soon.
Our main focus will be on primary tumors, however I am not a clinician and medical issues may be better addressed to Katie Mannix, our Clinical Manager at CMannix@partners.org.
MSPH Business Manager / Research Grants Manager
Northeast Proton Therapy Center (NPT-100)
Massachusetts General Hospital
Dept. of Radiation Oncology
Boston, MA 02114
(617) 724-9640 (617) 724-9532 FAX
compiled by doctordee
updated November 2003
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