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Proton therapy is a type of particle therapy which utilizes a beam of protons to irradiate diseased tissue, most often in the treatment of cancer. Terapia adronica]] Particle therapy is a form of External beam radiotherapy utilizing beams of protons, neutrons, or atomic nuclei. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Irradiation is the process by which an item is exposed to Radiation.

Contents

Description

Proton therapy, like all forms of radiotherapy, works by aiming energetic ionizing particles (in this case, protons accelerated with a particle accelerator) onto the target tumor. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive [1] These particles damage the DNA of cells, ultimately causing their death. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Cancerous cells, because of their high rate of division and their reduced ability to repair damaged DNA, are particularly vulnerable to attack on their DNA. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells.

Due to their relatively enormous size, protons scatter less easily in the tissue and there is very little lateral dispersion; the beam stays focused on the tumor shape without much lateral damage to surrounding tissue. All protons of a given energy have a certain range; no proton penetrates beyond that distance. [1] Furthermore, the dosage to tissue is maximum just over the last few millimeters of the particle’s range; this maximum is called the Bragg Peak. The Bragg curve plots the energy loss of Ionizing radiation during its travel through matter This depth depends on the energy to which the particles were accelerated by the proton accelerator, which can be adjusted to the maximum rating of the accelerator. It is therefore possible to focus the cell damage due to the proton beam at the very depth in the tissues where the tumor is situated; tissues situated before the Bragg peak receive some reduced dose, and tissues situated after the peak receive none. [2]

Early history of proton therapy

The first suggestion that energetic protons could be an effective treatment method was made by Robert R. Wilson in a paper published in 1946 while he was involved in the design of the Harvard Cyclotron Laboratory (HCL). Robert Rathbun Wilson ( March 4, 1914 &ndash January 16, 2000) was an American Physicist who was a group leader of the Manhattan The first treatments were performed at Particle accelerators built for physics research, notably Berkeley Radiation Laboratory in 1954 and at Uppsala in Sweden in 1957. The Ernest Orlando Lawrence Berkeley National Laboratory ( LBNL) is a U In 1961, a collaboration began between HCL and the Massachusetts General Hospital (MGH) to pursue proton therapy. Massachusetts General Hospital ( Mass General or MGH) is a Teaching hospital of Harvard Medical School and a Biomedical research Over the next 41 years, this program refined and expanded these techniques while treating 9,116 patients before the Cyclotron was shut down in 2002. Following this pioneering work, the first hospital based proton treatment center in the United States was built in 1990 at the Loma Linda University Medical Center in Loma Linda, California (LLUMC) (recently renamed the James M. Loma Linda University Medical Center ( LLUMC) is a teaching hospital of Loma Linda University School of Medicine in Loma Linda, California, United Slater Proton Therapy Center). This was followed by The Northeast Proton Therapy Center at Massachusetts General Hospital (recently renamed the Francis H. Burr Proton Therapy Center), to which the HCL treatment program was transferred during 2001 and 2002.

Pros and cons

The treatment method is of interest because of its ability to accurately target and kill tumors, both near the surface and deep seated within the body, while minimizing damage to the surrounding tissue. [1] For this reason, it is favored for treating certain kinds of tumors where conventional X-ray radiotherapy would damage surrounding radio-sensitive tissues to an unacceptable level. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant [1] This is of particular importance in the case of pediatric patients where long term side effects such as residual occurrence of secondary tumors resulting from the overall radiation dose to the body are of great concern. Because of the lower dose to healthy tissue protons have less severe collateral side-effects than conventional radiation therapy. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant

The logic for treating common cancers (for example lung, head/neck, etc) with proton therapy is the same as saying that surgery alone should cure most cancers, as surgery is the Definitive Local Treatment. Surgery (from the χειρουργική cheirourgikē, via chirurgiae meaning "hand work" is a medical specialty that uses operative manual and instrumental Of course, surgery does not - because most cancers spread microscopically very early beyond the tumor ('local') site.

Historically, one area where proton therapy had considerable early successful application was in treating choroidal malignant melanomas, a type of eye cancer for which the only known treatment was enucleation (removal of the eye). The choroid, also known as the choroidea or choroid coat, is the vascular layer of the Eye lying between the Retina and the Sclera Melanoma is a Malignant Tumor of Melanocytes which are found predominantly in skin but also in the Bowel and the Eye (see Enucleation is removal of the Eye, leaving the eye muscles and remaining orbital contents intact Today, proton therapy is one of the techniques that are capable of treating this tumor without mutilation. Proton therapy is used on cancers that have not yet spread. [3]

Implementation

2005 image of the control panel of the synchrocyclotron at the Orsay proton therapy center
2005 image of the control panel of the synchrocyclotron at the Orsay proton therapy center

Proton therapy, however, needs heavy equipment - weighing into the hundreds of tons. [1] For instance, the Orsay proton therapy center, in France, uses a synchrocyclotron weighing 900 tons in total. A synchrocyclotron is a Cyclotron in which the frequency of the driving RF electric field is varied to compensate for the mass gain of the accelerated particles as their velocity Such equipment was formerly only available within centers studying particle physics; and in the case of the Orsay installation, the treatment machine was converted from particle research usage to medical usage. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them

Proton therapy for ocular tumors is also available in Sacramento at the UC Davis Proton Facility, a facility operated exclusively by the UC San Francisco Department of Radiation Oncology. It is estimated that over 44,000 patients have been effectively treated with proton therapy. With nearly 5000 patients, the largest number of ocular tumors have been treated since 1984 at the Paul Scherrer Institute in Switzerland. The Paul Scherrer Institute (PSI is a multi-disciplinary research institute which belongs to the Swiss ETH-Komplex covering also the ETH Zurich and EPFL

Now on line as well is the Midwest Proton Radiotherapy Institute at Indiana University. In the summer of 2006 treatment started at two new facilities: University of Texas M. D. Anderson Cancer Center[4] in Houston, Texas, and the University of Florida Proton Therapy Institute in Jacksonville, Fla. The University of Texas M D Anderson Cancer Center is one of the nation's original three comprehensive Cancer centers established by the National Cancer Act of 1971 (This particular proton therapy center is unique in that it is the only facility that sits at grade, or at ground-level. In centers prior to this, the first floor which contains the proton cyclotron is situated below ground to aide in radiation shielding. Due to the high water table in Florida, the entire building was raised to ground level and the exterior walls thickened to 18 feet in some areas to obtain the same level of radiation shielding. ) The University of Pennsylvania is slated to open the biggest proton therapy institute in the world (the Roberts Proton Therapy Center in the Perelman Center for Advanced Medicine) in 2009. The University of Pennsylvania (also known as Penn) is a private University located in Philadelphia, Pennsylvania, USA. The last three facilities were designed by the architecture firm Tsoi/Kobus and Associates and the proton therapy equipment supplier was Ion Beam Applications (IBA).

In July 2007, Central DuPage Hospital (CDH) in Winfield, Ill. announced its intent to enter a joint venture with ProCure Treatment Centers Inc. and Radiation Oncology Consultants, Ltd. to bring the future of cancer treatment to Illinois. Patient treatment is expected to begin at CDH by 2010. In a similar partnership, Procure is building a proton therapy center in Oklahoma City, OK which should be online in 2009-2010. Both sites are being designed by Tsoi/Kobus and use proton therapy equipment supplied by IBA.

However, there are now several dedicated proton therapy centers in operation or under construction in North America, Europe, and Asia. Proton beam radiation therapy has had remarkable success in the treatment of many types of cancer, including brain and spinal tumors, as well as prostate cancer. Some researchers have suggested that antiprotons may be even more effective at killing cancer cells than their proton counterparts. The antiproton ( pronounced p-bar) is the Antiparticle of the Proton. So far, only initial research with cell cultures has been performed. Cell culture is the process by which prokaryotic, or eukaryotic cells are grown under controlled conditions [5][6]

Future proton centers

Highlighting the growing recognition, progress, and degree of potential for Proton Beam treatment, there are several new centers in the advanced planning stage within the U. S. , most requiring an investment of $120 million to $200 million:

The future promises even more exciting developments. The great hindrance to universal use of the proton in cancer treatment is the size and cost of the cyclotron or synchrotron equipment necessary. The Massachusetts Institute of Technology (MIT) in collaboration with an industrial team, is working on development of a comparatively small accelerator system to deliver the proton therapy to patients. When perfected, an even more rapid expansion of proton facilities should almost immediately occur. The St. Louis, Missouri facility, and the two Florida hospitals mentioned above are each planning to use one of these systems. The Oklahoma City site will use a cyclotron developed by IBA.

Therapy equipment suppliers

Following firms are currently supplying or developing proton therapy equipment: the market leader is IBA (Belgium), Still River Systems USA, Optivus Proton Therapy USA, Hitachi (Japan), ACCEL (Germany, now acquired by Varian, USA), [7]

Footnotes

2. () is a Multinational corporation specializing in high-technology and services headquartered in Marunouchi Itchome Chiyoda, Tokyo, Japan. James Metz. “Differences Between Protons and X-rays” The Abramson Cancer Center of the University of Pennsylvania. Accessed February2, 2008.

References

  1. ^ a b c d e "Zap! You're not dead. " Economist, 2007-09-08. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 70 - Roman forces under Titus sack Jerusalem. 1264 - The Statute of Kalisz 384 (8545):13-14
  2. ^ Metz, James. "Differences Between Protons and X-rays", The Abramson Cancer Center of the University of Pennsylvania, 2006-07-31. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 30 BC - Battle of Alexandria: Mark Antony achieves a minor victory over Octavian 's forces but most of his army subsequently Retrieved on 2008-02-04. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 211 - Roman Emperor Septimius Severus dies leaving the Roman Empire in the hands of his two quarrelsome sons  
  3. ^ http://www.snof.org/maladies/melanome-oculaire.html article in French Template:Icon fr
  4. ^ Health Care Renewal: M. D. Anderson Cancer Center Leases Its Name
  5. ^ CERN Bulletin
  6. ^ Elsevier Article Locator
  7. ^ Microsoft PowerPoint - AAPM_Lomax.ppt [Read-Only]
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