In the field of medical procedures, Proton therapy , or proton light therapy is a type of particle therapy that uses proton beams to illuminate diseased tissue, most often in cancer care. The main advantage of proton therapy compared to other types of external beam radiotherapy is that as charged particles, the doses are stored above the narrow range and there is minimal dose out.
Video Proton therapy
Description
Proton therapy is a type of external radiotherapy that uses ionizing radiation. In proton therapy, medical personnel use particle accelerators to target tumors with proton beams. These charged particles damage cell DNA, eventually killing them or stopping their reproduction. Cancer cells are particularly vulnerable to attacks on DNA because of their high cleavage rate and reduced ability to repair DNA damage. Some cancers with specific defects in DNA repair may be more sensitive to proton radiation.
Because of their relatively large mass, protons have few side-edges that spread in tissues; the rays of light do not widen much, remain focused on the shape of the tumor and only provide low-dose side effects to surrounding tissues. All protons of given energy have a certain penetration range; very few protons penetrate beyond that distance. Furthermore, the doses sent to the tissues are maximized only over the last few millimeters of the particle range; This maximum is called the peak of Bragg, often referred to as SOBP.
To treat the tumor at a greater depth, the proton accelerator must produce a ray with a higher energy, usually given in eV or electron volts. The accelerators used for proton therapy usually produce protons with energy in the range of 70 to 250 MeV. Adjusting the proton's energy during the treatment maximizes cellular damage that causes proton rays inside the tumor. Tissues closer to the surface of the body than tumors that receive reduced radiation, and therefore reduce damage. Deeper tissues in the body receive very few protons, so the dose becomes immeasurably small.
In most treatments, different energy protons with the Bragg peaks at different depths are applied to treat the entire tumor. This Bragg peak is displayed as a thin blue line in the image on the right. The total radiation dose of the proton is called spread-out Bragg peak (SOBP), indicated as a heavy dashed blue line in the image on the right. It is important to understand that, while the tissue behind (or deeper than) the tumor receives virtually no radiation from proton therapy, the tissue in front (more superficially than) the tumor receives a radiation dose based on SOBP.
Tools
Most of the installed proton therapy systems utilize the isocron cyclotron. The cyclotron is considered simple to operate, reliable and can be made compact, especially with the use of superconducting magnets. Synchrotrons can also be used, with the advantage of easier production on a variety of energies. Linear accelerators, such as those used for photon radiation therapy, become commercially available due to size and cost issues resolved.
Maps Proton therapy
History
The first suggestion that energetic protons could be an effective treatment method was made by Robert R. Wilson in a paper published in 1946 when he was involved in the design of the Harvard Cyclotron Laboratory (HCL). The first treatment was performed with particle accelerators built for physics research, notably the Berkeley Radiation Laboratory in 1954 and in Uppsala in Sweden in 1957. In 1961, a collaboration began between HCL and Massachusetts General Hospital (MGH) to pursue proton therapy. Over the next 41 years, the program refined and expanded these techniques while treating 9116 patients before the cyclotron was discontinued in 2002. The world's first hospital-based proton therapy center in the world is a low-energy cyclotron center for ocular tumors at the Clatterbridge Center for Oncology at England, opened in 1989, followed in 1990 at Loma Linda University Medical Center (LLUMC) in Loma Linda, California. Subsequently, the Norton Proton Therapy Center at Massachusetts General Hospital was brought online, and the HCL treatment program was transferred there during 2001 and 2002. In 2010 the facility joined the addition of seven regional hospital-based proton therapy centers in the United States. alone, and more around the world.
Apps
Doctors use protons to treat conditions in two broad categories:
- Disease sites that respond well to higher radiation doses, ie, dose escalation. In some cases, dose escalation has shown higher probability of "healing" (ie local control) than conventional radiotherapy. These include, among others, uveal melanoma (ocular tumor), skull base and paraspinal tumor (chondrosarcoma and chordoma), and an inoperable sarcoma. In all these cases, proton therapy achieved a significant improvement in the probability of local control over conventional radiotherapy. In the treatment of ocular tumors, proton therapy also has a high level in maintaining the natural eye.
- Treatment where increased precision of proton therapy reduces unwanted side effects by reducing the dose to normal tissue. In this case, the tumor dose is the same as conventional therapy, so there is no hope of a possible increase in the cure of the disease. Instead, the emphasis is on reducing the integral dose to normal tissue, thereby reducing unwanted effects.
Two prominent examples are childhood neoplasms (such as medulloblastoma) and prostate cancer.
Pediatric care
The irreversible long-term side effects of conventional radiation therapy for pediatric cancer have been well documented and include growth disturbances, neurocognitive toxicity, ototoxicity with subsequent effects on language learning and development, and renal dysfunction, endocrine and gonad. Radiation-induced secondary irritation is a very serious side effect that has been reported. Because there is no out dose when using proton radiation therapy, the dose for surrounding normal tissue can be very limited, reducing acute toxicity that positively impacts the long-term side effects. Cancers that require craniospinal irradiation, for example, benefit from the absence of an exit dose with proton therapy: doses for the heart, mediastinum, intestines, bladder and other anterior tissues to the spine are removed, resulting in acute thoracic, gastrointestinal and bladder reduction.
Prostate cancer
In the case of prostate cancer, the problem is less clear. Several published studies have found a decrease in long-term rectal and genito-urinary damage when treated with protons rather than photons (meaning X-rays or gamma-ray therapy). Others show a small difference, confined to cases where the prostate is very close to a particular anatomical structure. The relatively small increase found may be the result of inconsistent patient regulation and internal organ movement during treatment, which offsets most of the advantages of increased accuracy. One source indicates that a dose error of about 20% can result from a motion error of only 2.5 mm (0.098 in). and the other that the prostate movement is between 5-10 mm (0.20-0.39 in).
However, the number of cases of prostate cancer diagnosed each year far exceeds that of other diseases mentioned above, and this has caused some, but not all, facilities to devote the majority of their care slots for prostate treatment. For example, two hospital facilities devote about 65% and 50% of their proton treatment capacity to prostate cancer, while one-third requires only 7.1%.
Overall figures around the world are difficult to compile, but one example states that in 2003 about 26% of proton therapy treatments worldwide were for prostate cancer.
Eye tumor
Proton therapy for ocular (eye) tumors is a special case because this treatment requires only relatively low energy protons (about 70 MeV). Because of this low energy requirement, some particle therapy centers only treat ocular tumors. Proton, or more generally, hadron therapy near eye tissue provides a sophisticated method for assessing eye alignment that can vary significantly from other patient position verification approaches in guided particle image therapy. Position and correction verification should ensure that radiation saves sensitive tissue such as the optic nerve to maintain the patient's vision.
Head and neck tumor
The proton particles do not deposit the exit dose, allowing proton therapy to rescue normal tissues distal to the target tumor. It is very useful for treating tumor head and neck due to anatomic constraints faced almost on all cancers in this region. The unique dosimetric advantage for proton therapy translates into reduction of toxicity. For recurrent head and neck cancer that require reirradiation, proton therapy is able to maximize the radiation dose focused on the tumor while minimizing the dose to the surrounding tissue resulting in a minimal acute toxicity profile, even in patients who have received some previous radiotherapy programs.
Although chemotherapy is the main treatment for patients with lymphoma, consolidative radiation is often used in Hodgkin's lymphoma and aggressive non-Hodgkin's lymphoma, while definitive treatment with radiation alone is used in a small proportion of lymphoma patients. Unfortunately, treatment-related toxicity caused by chemotherapy agents and radiation exposure to healthy tissue is a major problem for lymphoma patients. Advanced radiation therapy technologies such as proton therapy may offer significant clinical and relevant benefits such as saving important organs at risk and lowering the risk of delayed late tissue damage while still achieving the primary goal of disease control. It is very important for lymphoma patients who are being treated with curative intentions and have a long life expectancy after therapy.
Gastrointestinal malignancy
The increasing amount of data reported has shown that proton therapy has great potential to increase therapeutic tolerance for patients with GI malignancy. The possibility of decreasing radiation doses to risky organs can also help facilitate increased doses of chemotherapy or enable new chemotherapy combinations. Proton therapy will play a decisive role in the context of ongoing intensive combined modal care for GI cancer. The following reviews present the benefits of proton therapy in treating hepatocellular carcinoma, pancreatic cancer and esophageal cancer.
Comparison with other treatments
The question of when, whether and how best to apply this technology is controversial. In 2012 there were no controlled trials to demonstrate that proton therapy resulted in increased survival or other clinical outcomes (including impotence in prostate cancer) compared with other types of radiation therapy, although a five-year study of prostate cancer was being conducted at Massachusetts General. HOSPITAL.
Proton therapy is much more expensive than conventional therapy. In 2012 proton therapy requires enormous capital investment (from US $ 100 million to over $ 180 million).
Preliminary results from a 2009 study, including high-dose treatments, showed very few side effects.
NHS Options have stated:
We can not say with confidence that proton-ray therapy is better than radiotherapy. (...) Some overseas clinics providing proton rays greatly market their services to parents who are desperate to get care for their children. Proton ray therapy can be very expensive and it is not clear whether all children treated abroad are treated appropriately.
X-ray radiotherapy
The image on the right of the page shows how X-ray rays (IMRT, left frame) and proton blocks (right frame), different energies, penetrate human tissue. Tumors of considerable thickness are covered by IMRT spreading Bragg peak (SOBP) shown as red line distribution in the image. SOBP is the overlap of some pure Bragg peaks (blue lines) at a staggered depth.
Megavoltage X-ray therapy has less "potential for skin scarring" than proton therapy: X-ray radiation in the skin, and at very small depths, is lower than proton therapy. One study estimated that the passively dispersed proton field had a slightly higher dose of entry in the skin (~ 75%) than the megavoltage photon (MEV) photon beam (~ 60%). The dose of X-ray radiation falls gradually, damaging deeper tissues inside the body and damaging the skin and surface tissues opposite the entrance of the jets. The difference between the two methods depends on:
- SOBP width
- Depth of tumor
- Number of blocks that treat tumors
The advantages of X-rays reducing damage to the skin at the entrance are partially eliminated by skin damage at the exit point.
Because X-ray treatments are usually done with multiple exposures from opposite sides, each part of the skin is exposed both in and out of the X-rays. In proton therapy, skin exposure at the entry point is higher, but tissue on the opposite side from the body to the tumor does not receive radiation. Thus, X-ray therapy causes less damage to the skin and surface tissue, and proton therapy causes less damage to the deeper tissues ahead and beyond the target.
An important consideration in comparing this treatment is whether the equipment provides protons through the scattering method (historically, the most common) or spot scanning method. Spot scanning can adjust the width of SOBP based on spot-by-spot, which reduces normal (healthy) tissue volume in high dose areas. In addition, spot scanning allows for the modulation of proton intensity (IMPT), which determines the intensity of individual points using an optimization algorithm that allows users to balance competing objectives of radiation tumors while saving normal tissue. The availability of spot scanning depends on machines and institutions. Spot scanning is better known as pencil ray scanning and is available at IBA, Hitachi, Mevion (known as hyperscan and not US FDA approved by 2015) and Variants.
Surgery
Doctors base decisions to use proton surgery or therapy (or any radiation therapy) on tumor type, stage, and location. In some cases, surgery is superior (such as skin melanoma), in some cases higher radiation (such as skull base chondrosarcoma), and in some cases they are comparable (eg, prostate cancer). In some cases, they are used together (eg, early rectal cancer or breast cancer). The benefit of external proton beam radiation lies in the dosimetric difference of external X-ray radiation and brachytherapy in cases where radiation therapy is already indicated, rather than as a direct competition with surgery. However, in the case of prostate cancer, the most common indication for proton beam therapy, no direct clinical study comparing proton therapy with surgery, brachytherapy, or other treatments has demonstrated a clinical benefit for proton-beam therapy. Indeed, the largest study to date suggests that IMRT compared with proton therapy is associated with fewer gastrointestinal morbidities.
Side effects and risks
Proton therapy is a type of external beam radiotherapy, and shares the risks and side effects of other forms of radiation therapy. However doses outside the treatment area can be significantly lower for deep tissue tumors than X-ray therapy, since proton therapy takes full advantage of the Bragg peak. Proton therapy has been used for more than 40 years, and is a mature treatment technology. However, as with all medical knowledge, an understanding of the interaction of radiation (protons, X-rays, etc.) With tumors and normal tissue is still not perfect.
Cost
Historically, proton therapy has been expensive. An analysis published in 2003 determined the relative cost of proton therapy by about 2.4 times that of X-ray therapy. However, newer and more compact proton jets can be 4-5 times cheaper and offer more accurate three-dimensional targeting. Thus the cost is expected to decrease as better proton technology becomes more available. An analysis published in 2005 determined that the cost of proton therapy was unrealistic and should not be a reason to deny patients access to technology. In some clinical situations, the proton-light therapy is clearly superior to the alternative.
A 2007 study expressed concern about the effectiveness of proton therapy for treating prostate cancer, but with the advent of new developments in technology, such as better scanning techniques and more precise dosing ('pencil glow'), the situation may change. very. Amitabh Chandra, a health economist at Harvard University, stated, "Proton-beam therapy is like a death star of American medical technology... It is a metaphor for all the problems we face in American medicine." However, other studies have shown that proton therapy actually carries cost savings. The emergence of the second generation, and much cheaper, proton therapy equipment that emerged in 2012 can change opinions.
Treatment center
As of July 2017, there are more than 75 particle therapy facilities around the world, with at least 41 others under development. By the end of 2015 more than 154,203 patients have been treated.
One obstacle to the universal use of protons in the treatment of cancer is the size and cost of the required cyclotron or synchrotron equipment. Some industry teams work on developing a relatively small accelerator system to provide proton therapy to patients. Among the technologies under investigation are superconducting synchrocyclotrons (also known as FM Cyclotrons), ultra-compact synchrotrons, dielectric wall accelerators, and linear particle accelerators.
United States
Proton treatment centers in the United States in 2017 (in chronological order of first treatment date) include:
The University of Indiana's Proton Health Therapy Center in Bloomington, Indiana opened in 2004 and ceased operations in 2014.
Outside the US
United Kingdom
In 2013 the British government announced that Ã, Â £ 250 million has been budgeted to build two advanced radiotherapy centers, to open in 2018 at the Christie NHS Foundation Trust Hospital in Manchester and the University College London Hospital NHS Foundation Trust. It will offer high-energy proton therapies, currently not available in the UK, as well as other types of advanced radiotherapy, including intensity-modulation radiotherapy (IMRT) and imaging radiotherapy (IGRT). In 2014, only low-energy proton therapy is available in the UK, at the NHS Foundation Trust Clatterbridge Cancer Center in Merseyside. But the NHS UK has paid to have suitable cases treated abroad, mostly in the US. Such cases have increased from 18 in 2008 to 122 in 2013, 99 of whom are children. The cost for National Health Service averages around Ã, Â £ 100,000 per case.
In January 2015, it was announced that the UK would get the first energy-beam energy proton therapy center a year earlier than expected. A company called Advanced Oncotherapy signed an agreement with Howard de Walden Estate to install a machine at Harley Street, the heart of private medicine in London, to be ready by 2017. The company promises that the use of linear accelerators allows for a one-third smaller facility and one-fifth of the cost of facilities based on design existing cyclotron.
Proton Partners International developed three centers in Newport, Wales, Bomarsund, Northumberland, and Reading, Berkshire which is expected to open in 2017.
See also
- Particle therapy
- Particle charged therapy
- Hadron
- Microbes
- Rapid neutron therapy
- Boron neutron retention therapy
- Linear energy transfer
- Electromagnetic radiation and health
- Dosimetry
- Ionizing radiation
- Glossary of oncology-related terms
References
77 Bortfeld, Thomas R. and Jay S. Loeffler (2017) Three ways to make proton therapy affordable. Nature 549, 451-453 (28 September 2017) doi: 10.1038/549451a
Further reading
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Greco C.; Wolden S. (Apr 2007). "Current radiotherapy status with proton and beam ion light". Cancer . 109 (7): 1227-38. doi: 10.1002/cncr.22542. PMID 17326046. - A.M. Koehler, W.M. Preston, "Proton in Radiation Therapy: Comparative Dose Distribution for Proton, Photon, and Electron Radiology 104 (1): 191-195 (1972).
- "Bragg Peak Proton Radiosurgery for Brain Arteriovenation Malformations" R.N. Kjelberg, presented at First Int. Seminar on the Use of Proton Beams in Radiation Therapy, Moscow (1977).
- Austin-Seymor, M.J. Munzenrider, et al. "Proton Radiation Therapy Fractionation of Tumor Tumors and Intracraine Tumors" Am. J. of Clinical Oncology 13 (4): 327-330 (1990).
- "Proton Radiotherapy", Hartford, Zietman, et al. in Radiotheraputic Management of Prostate Carcinoma , A. D'Amico and G.E. Hanks. London, UK, Arnold Publishers: 61-72 (1999).
External links
- Proton therapy - MedlinePlus Medical Encyclopedia
- Proton Therapy "Proton therapy will come to England, but what does it mean to patients?", Arney, Kat, Science blog, Cancer Research UK, 16 September 2013
- Proton Therapy in Korea
Source of the article : Wikipedia
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