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Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant cancer treatment. It is often used as a palliative treatment, where cure is not possible and the aim is for local disease control or symptomatic relief. Total body irradiation (TBI) is a special radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has a few applications in non-malignant conditions, such as the treatment of severe thyroid eye disease, pterygium, prevention of keloid scar growth, and prevention of heterotopic bone formation. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers. Medicine is a branch of health science concerned with maintaining human health and restoring it by treating disease and injury; it is both an area of knowledge, a science of body organ system|systems and diseases and their treatment, and the applied practice of that knowledge. ...
Ionizing radiation is a type of particle radiation in which an individual particle (for example, a photon, electron, or helium nucleus) carries enough energy to ionize an atom or molecule (that is, to completely remove an electron from its orbit). ...
When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ...
Look up Therapy on Wiktionary, the free dictionary Therapy (in Greek: θεÏαπεία) or treatment is the attempted remediation of a health problem, usually following a diagnosis. ...
Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ...
Chest X-ray Radiology traditionally was the branch of medical science dealing with the medical use of X-rays emitted by X-ray machines or other such radiation devices for the purpose of obtaining visual information as part of medical imaging. ...
Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. ...
Diagnosis (from the Greek words dia = by and gnosis = knowledge) is the process of identifying a disease by its signs, symptoms and results of various diagnostic procedures. ...
Palliative care is any form of medical care or treatment that concentrates on reducing the severity of the symptoms of a disease or slows its progress rather than providing a cure. ...
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Graves-Basedow disease is a form of thyroiditis, an autoimmune disorder that stimulates the thyroid gland, being the most common cause of hyperthyroidism (overactivity of the thyroid). ...
A pterygium, meaning wing, is a benign growth of the conjunctiva. ...
A keloid scar is a special case of a scar. ...
Application Radiotherapy is commonly used for the treatment of tumors. It may be used as the primary therapy. It is also common to combine radiotherapy with surgery and/or chemotherapy and/or hormone therapy. Most common cancer types can be treated with radiotherapy in some way. These include breast cancer, prostate cancer, lung cancer, colorectal cancer, head & neck cancers, gynaecological tumors, bladder cancer and lymphoma, although the cancer's stage (progress) and invasion into lymph nodes, as well as other health and (unfortunately) monetary factors affect which treatment will have the greatest possibility of success. See the article about cancer for the main article about malignant tumors. ...
A typical modern surgery operation For other meanings of the word, see Surgery (disambiguation) Surgery (from the Greek cheirourgia - lit. ...
Chemotherapy is the use of chemical substances to treat disease. ...
In medicine, hormone therapy is the use of hormones in medical treatment and covers various types of hormones including growth hormones and sex hormones. ...
Breast cancer is cancer of breast tissue. ...
Prostate cancer is a group of cancerous cells (a malignant tumor) that begins most often in the outer part of the prostate. ...
The incidence of lung cancer is highly correlated with smoking. ...
Diagram of the stomach, colon, and rectum Colorectal cancer, also called colon cancer or bowel cancer, includes cancerous growths in the colon, rectum and appendix. ...
Head and neck cancers are malignant growths located in the oral cavity (mouth), nasal cavity, pharynx, larynx, paranasal sinuses, salivary glands and lymph nodes of the upper neck. ...
Cystoscopic view of a papillary bladder tumor (top); the bladder wall is visible on the bottom right Bladder cancer refers to any of several types of malignant growths of the urinary bladder. ...
Lymphoma is a general term for malignancies of lymphocytes or, more rarely, of histiocytes. ...
Stage has several meanings: Look up stage in Wiktionary, the free dictionary. ...
Radiation therapy is commonly applied just to the localised area involved with the tumor. Often the radiation fields also include the draining lymph nodes. It is possible to give radiotherapy to the whole body TBI, or entire skin surface. See the article about cancer for the main article about malignant tumors. ...
TBI may mean: Traumatic brain injury Total body irradiation Tennessee Bureau of Investigation This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ...
In order to spare normal tissues (such as skin or organs which radiation must pass through in order to treat the tumor) several angles of exposure are utilized such that the radiation beams overlap on top of each other at the tumor, providing a much larger absorbed dose there than in the surrounding, healthy tissue.
Side Effects Radiotherapy is in itself painless. Many low-dose palliative treatments (e.g. radiotherapy to bony metastases) cause minimal or no side effects. Treatment to higher doses causes variable side effects during treatment (acute side effects) or in the months to years following treatment (long term side effects.) The nature of the side effects depends on the site which receives the radiation, and the treatment schedule (type of radiation, dose, fractionation, concurrent chemotherapy.) Individuals differ somewhat in their radiation reaction. Retreatment of previously irradiated sites can cause particular problems: any tissue has a maximum lifetime tolerance for radiation, so retreatment of a site which received a maximum safe dose years before can cause problems.
Most side effects are predictable and expected. One of the aims of modern radiotherapy is to reduce side effects to a minimum, and to help the patient to understand and to deal with those side effects which are unavoidable.
Acute Side Effects - Damage to epithelial surfaces (skin, oral, pharyngeal and bowel mucosa, urothelium)
- The rate of onset and recovery is related to the rate of turnover of the epithelial cells. Typically the skin starts become pink and sore one week to ten days into treatment. The reaction may become more severe during the treatment and for up to about one week following the end of radiotherapy, and there may be moist desquamation (where the skin breaks down). Although this is uncomfortable, recovery is usually quite quick. Skin reactions tend to be worse in areas where there are natural folds in the skin, such as underneath the female breast, behind the ear, and in the groin.
- Similarly, the lining of the mouth, throat, esophagus, and bowel will be affected by radiation. If the head and neck area is treated, temporary soreness and ulceration commonly occur in the mouth and throat. If severe, this can affect swallowing, and the patient may need painkillers and nutritional support. The esophagus can also get sore if it is treated directly, or if, as commonly occurs, it receives a dose of radiation during treatment of lung cancer.
- The lower bowel may be treated directly with radiation (treatment of rectal or anal cancer) or be exposed as an inevitable side effect of radiotherapy to other pelvic structures (prostate, bladder, female genital tract.) Apart from soreness, diarrhea is commonly seen, and nausea may be a problem.
- Swelling (oedema)
- As part of the general inflammation that occurs, swelling of soft tissues may cause problems during radiotherapy. This is a concern during treatment of brain tumours and brain metastases especially where there is pre-existing raised intracranial pressure, and also where the tumour is causing near-total obstruction of a lumen (eg: trachea or main bronchus). Surgical intervention may be considered prior to treatment with radiation. If surgery is not felt necessary or appropriate, the patient may receive steroids during radiotherapy in order to reduce swelling.
- Infertility
- The gonads (ovaries and testicles) are very sensitive to radiation. They will be unable to produce gametes following direct exposure to most normal treatment doses of radiation.
- Generalized fatigue
In zootomy, epithelium is a tissue composed of a layer of cells. ...
Moist desquamation is a description of the clinical pattern seen in radiotherapy where the skin thins and then starts to weep because of loss of integrity of the epithelial barrier. ...
In anatomy, the lumen is the cavity or channel within a tube or tubular structure, such as the vascular lumen of a blood vessel, along which blood flows. ...
In chemistry and biology, Steroids are a type of lipid, characterized by a carbon skeleton with four fused rings. ...
A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis...
Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ...
Medium and Long-Term Side Effects These may be minimal and depend on the tissue which received the treatment. - Fibrosis
- Tissues which have been irradiated tend to become less elastic over time due to a diffuse scarring process.
- Hair loss
- This may be pronounced in patients who have received radiotherapy to the brain. For the most part, hair loss is limited to the area treated by the radiation. Unlike the hair loss seen with chemotherapy, radiation-induced hair loss is more likely to be permanent.
- Dryness
- The salivary glands and tear glands have a radiation tolerance of about 30Gy in 2Gy fractions, a dose which is exceeded by most radical head and neck cancer treatments. Dry mouth (xerostomia) and dry eyes (xerophthalmia) can be an irritating long-term problem. Similarly, sweat glands in treated skin (such as the armpit) tend to stop working, and the naturally moist vaginal mucosa is often dry following pelvic irradiation.
- Cancer
- Radiation is a cause of cancer, and secondary malignancies are seen in a small minority of patients, generally many years after they have received a curative course of radiation treatment. In the vast majority of cases, this risk is greatly outweighed by the reduction in risk conferred by treating the primary cancer.
GY Gy or gy may stand for: gray (unit) for absorbed dose of radiation (Gy) Guyana (ISO country code) Gy, Switzerland, a village in the canton of Geneva in Switzerland Gy, a commune in the Haute-Saône département in France 1 gigayear (1 billion years) (the preferred symbol...
Xerostomia is a medical term for dry mouth caused by a lack of saliva. ...
Xerophthalmia (Greek for dry eyes) is a medical condition in which the eye doesnt produce tears. ...
Dosage Radiation therapy, like drugs, has biological effects. It is therefore useful to distinguish the total dose from the fractionation schedule. Radiation therapy is usually given daily, the dose depends primarily on tumor type, but many other factors such as whether radiation is given alone or with chemotherapy, before or after surgery, the success of surgery and its findings and many other reasons that are considered by the treating doctor (known as a radiation oncologist). For Radical (curative) cases the typical dose for a solid epithelial tumor may range from 50 to 70 grays (Gy) or more, while lymphomas (white cell) tumors might receive doses closer to 20 to 40 Gy given in daily doses (a daily dose is a fraction); in adults these are typically 1.8 to 2 Gy per fraction. These small frequent doses allow healthy cells time to grow back, repairing damage inflicted by the radiation. In short, total dose can be given in daily fractions using external beam radiation or the total dose can be given via other methods such as implants that deliver radiation continuously over a given timeframe. Depending on the implant type, it may be given as a fraction (e.g. High Dose Rate HDR) over minutes or hours or as another example permanent seeds may be implanted (such as in the prostate) which slowly deliver radiation until the seeds become inactive. In Palliative cases a single dose of 6-10Gy may be given to painful superficial tumours i.e. a rib metastasis to relieve pain. The gray (symbol: Gy) is the SI unit of absorbed dose. ...
Fractionation Schedules As mentioned above, the typical fractionation schedule (in the USA & Europe) is 1.8 to 2 Gy per fraction, with 1 fraction/day. The typical treatment schedule is 5 days per week (no weekends). This schedule is also common in the South of England, whereas in the North of the UK fraction sizes are quite commonly 2.67 - 2.75 Gy per fraction (treating daily M - F), with a lesser number of total fractions. The reason for this is mainly a resource issue within the NHS, with Clinical Oncology departments having a much greater workload than the private clinics in Europe & the USA. Both fractionation schedules are effective, individual clinician preference and availability of resource are the deciding factors. (Longer schedules are common where payment is made to the clinic according to the number of treatment fractions delivered).There are other alternative fractionation schedules that have been tried. One of the best-known was the CHART (Continuous Hyperfractionated Accelerated RadioTherapy) regimen for lung cancer, which uses 3 smaller fractions per day in the treatment of lung cancer. Although reasonably successful, this can impose strains on the departments delivering the service, as it required multiple treatments everyday, including weekends. With an international shortage of qualified Radiation Therapists this is often difficult to sustain. Twice a day treatments have been tried for other sites, such as head and neck cancers. A special case of twice a day radiotherapy is the concomitant boost regimen.
In some paediatric cancers, fractionation schedules tend to give 1.5 - 1.7 Gy/fraction. The reason for this is that fractionation effects the balance between acute and late toxicity, and with smaller fractions late effects are less likely to occur and are less severe. Obviously late effects are of more concern in pediatric patients than adults.
How It Works Radiation therapy works by damaging the DNA of cells. The damage is caused by an electromagnetic, electron or proton beam directly or indirectly ionizing the atoms which make up DNA chain. Indirect ionization happens as a result of the ionization of oxygen, forming free radicals, which then damage the DNA. In the most common forms of radiation therapy, most of the radiation effect is through free radicals. Because cells have mechanisms for repairing DNA breakage, where the DNA is broken on both strands of the DNA are the most significant in modifying cell characteristics. Because cancer cells generally are undifferentiated and stem cell-like, they reproduce more, and have a diminished ability to repair sub-lethal damage compared to most healthy differentiated cells. The DNA damage is inherited through cell division, accumulating damage to the cancer cells, causing them to die or reproduce more slowly. Proton radiotherapy works by sending protons with varying kinetic energy to precisely stop at the tumor. Being researched is antiproton radiotherapy which would require fewer treatments than proton radiotherapy. Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ...
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In chemistry, radicals (often refered to as free radicals) are atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...
Mouse embryonic stem cells. ...
Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ...
Kinetic energy is energy that a body has as a result of its speed. ...
Implications Tumors don't repair the radiation damage as well as nonmalignant tissue.
Most cells, however, die only during a specific phase of cellular reproduction, which has many curious implications:
- Some slowly growing tumors (for example, prostate) may be treated best by not treating them at all, since the patient will likely die from other causes, such as old age, before the cancer kills.
- It is thought that tumors which outgrow their blood supply, causing a low-oxygen state known as hypoxia, are more resistant to the effects of radiation because they reproduce less frequently, and are not subject to indirect damage caused by free radicals produced by the ionisation of oxygen.
- Some brain tumors do not die at extremely high doses. It is an open subject as to the mechanism by which they survive, but perhaps they do not reproduce in the usual way.
Hypoxia has several meanings: Hypoxia is the lack of oxygen in tissues, see Hypoxia (medical) Hypoxia is the lack of oxygen in a water body leading to the death of organisms, see Hypoxia (water) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share...
Kinds of Radiation Therapy Three main divisions of radiotherapy are external beam radiotherapy (XBRT) or teletherapy, brachytherapy or sealed source radiotherapy and unsealed source radiotherapy. The differences relate to the position of the radiation source; external is outside the body, while sealed and unsealed source radiotherapy has radioactive material delivered internally. Brachytherapy sealed sources are usually extracted later, while unsealed sources may be administered by injection or ingestion. Proton therapy is a special case of external beam radiotherapy where the particles are protons. External beam radiotherapy is the most common form of radiotherapy where a patient lies on a couch and an external source of X-rays is pointed at a particular part of the body. ...
External beam radiotherapy is the most common form of radiotherapy where a patient lies on a couch and an external source of X-rays is pointed at a particular part of the body. ...
Sealed source radiotherapy or brachytherapy is the application of radiation from close range and is used for techniques where the radioactive source is placed inside the area requiring treatment. ...
Sealed source radiotherapy or brachytherapy or endocurietherapy is the application of radiation from close range and is used for techniques where the radioactive source is placed inside the area requiring treatment. ...
Unsealed source radiotherapy relates to the use of soluble forms of radioactive substances which are injected into the body. ...
Proton therapy is a kind of external beam radiotherapy where protons are directed to a tumor site. ...
Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ...
Roughly half of the 2500 worldwide radiotherapy clinics are in the US (as of 2001).
Conventional External Beam Radiotherapy This is the mainstay of external beam radiotherapy in most of the world. Conventional refers to the way the treatment is planned or simulated on a specially calibrated conventional diagnostic x-ray machine (or sometimes by eye), and to the usually well established arrangements of the radiation beams to acheive a desired plan. The aim of simulation is to accurately target or localise the volume which is to be treated. This technique is well established, and is generally quick and reliable. The worry is that some high-dose treatments may be limited by the radiation toxicity to normal structures which lay close to the target volume. An example of this problem is seen in radical radiotherapy to the prostate gland, where the sensitivity of the adjacent rectum can limit the dose which can safely be prescribed to such an extent that tumour control may not be acheivable with any degree of confidence. For this reason, conformal radiotherapy is becoming the standard treatment for a number of tumour sites.
Virtual Simulation, 3-Dimensional Conformal Radiotherapy, and Intensity-Modulated Radiotherapy The planning of radiotherapy treatment has been revolutionised by the ability to delineate tumours and adjacent normal structures in 3 dimensions using a specialised CT scanner and dedicated computer planning software. In its most basic form, virtual simulation, this process allows more accurate placement of conventional radiotherapy fields than is possible using conventional X-rays, where soft-tissue structures are often difficult to assess clearly. 3-Dimensional Conformal Radiotherapy (3DCRT) is an elaboration of this process, whereby the profile of each radiation beam is sculpted to fit the profile of the target from that beam's eye view (BEV) using a Multi-Leaf Collimator (MLC) and a variable number of beams. The aim of this process is to improve the therapeutic index of the radiotherapy. By conforming the radiotherapy treatment volume closely to the shape of the tumour, the relative toxicity of radiation to the surrounding normal tissues can be reduced, allowing a higher dose of radiation to be delivered to the tumour than would be possible using conventional techniques. [edit]
Intensity-Modulated Radiotherapy (IMRT) is an iteration of 3DCRT that employs dynamic multileaf collimation to shape not only the profile of the beam, but also to vary the intensity of the beam over its area. This may allow greater conformality than standard 3DCRT. It also provides the novel ability to conform the treatment volume to concave surfaces. This may be useful if the tumour is wrapped around a vulnerable structure such as the spinal cord, where a therapeutic dose of radiation might otherwise cause unacceptable damage.
3DCRT is used extensively. IMRT is becoming more widely used but is limited by the fact that it is a very resource-intensive process, in terms of manpower and computing time. The proven benefits from both of these modalities over conventional radiotherapy in terms of improved overall survival are limited to a few tumour sites. There has been some concern about increased exposure of normal tissues to radiation, particularly with IMRT, and the potential for secondary radiation-induced malignancy. The downside of tight conformality is that there is an increased chance of geographically missing disease, which may be invisible on the planning scans (and therefore not included in the treatment plan) or which may move between treatments, either because of internal organ movement (such as respiration) or because of inadequate patient immobilisation. Whatever the criticisms of conventional radiotherapy, it gives a wider margin for error than conformal techniques.
Image Guided Radiation Therapy Image Guided Radiation Therapy (IGRT) machines have a CT scanner integrated with the treatment system, or an X-Ray Tube and aSi-detector mounted on the gantry of the linear accelerator. The patient can be scanned and the tumour located in 3D space immediately before treatment. The ability to correct for movement and setup errors allows smaller margins to be used, sparing healthy tissue and escalating the tumour dose. First systems using ultrasound for guidance are on the market. Using ultrasound instead of CT has the advantages of a higher soft tissue contrast, no additional ionizing radiation and cost efficient application. Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ...
See also When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ...
Chemotherapy is the use of chemical substances to treat disease. ...
Surgical Oncology is the branch of surgery which focuses on the surgical managment of malignant neoplasms (cancer). ...
Radiosurgery is a medical procedure which allows non-invasive brain surgery, i. ...
Dosimetry is the measurement of doses in matter and tissue from ionizing radiation, or radioactivity as it is popularly known. ...
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