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Definition:
Radiotherapy is a way of treating or managing cancer using radiation. It works by damaging cells in the area being treated. Normal cells are able to repair this damage, but cancer cells can’t and are destroyed.
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Radiation therapy is commonly applied to the cancerous tumor because of its ability to control cell growth. Ionizing radiation works by damaging the DNA of exposed tissue, furthermore, it is believed that cancerous cells may be more susceptible to death by this process as many have turned off their DNA repair machinery during the process of becoming cancerous. To spare normal tissues (such as skin or organs which radiation must pass through in order to treat the tumor), shaped radiation beams are aimed from several angles of exposure to intersect at the tumor, providing a much larger absorbed dose there than in the surrounding, healthy tissue. Besides the tumour itself, the radiation fields may also include the draining lymph nodes if they are clinically or radiologically involved with tumor, or if there is thought to be a risk of subclinical malignant spread. It is necessary to include a margin of normal tissue around the tumor to allow for uncertainties in daily set-up and internal tumor motion. These uncertainties can be caused by internal movement (for example, respiration and bladder filling) and movement of external skin marks relative to the tumor position.
Radiation oncology is the medical specialty concerned with prescribing radiation, and is distinct from radiology, the use of radiation in medical imaging and diagnosis). Radiation may be prescribed by a radiation oncologist with intent to cure (“curative”) or for adjuvant therapy. It may also be used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit and it can be curative). It is also common to combine radiation therapy with surgery, chemotherapy, hormone therapy, Immunotherapy or some mixture of the four. Most common cancer types can be treated with radiation therapy in some way. The precise treatment intent (curative, adjuvant, neoadjuvant, therapeutic, or palliative) will depend on the tumor type, location, and stage, as well as the general health of the patient. Total body irradiation (TBI) is a radiation therapy technique used to prepare the body to receive a bone marrow transplant. Brachytherapy, in which a radiation source is placed inside or next to the area requiring treatment, is another form of radiation therapy that minimizes exposure to healthy tissue during procedures to treat cancers of the breast, prostate and other organs.
Radiation therapy has several applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, pigmented villonodular synovitis, and prevention of keloid scar growth, vascular restenosis , and heterotopic ossification. The use of radiation therapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers.
Method of radiotherapy
Radiotherapy can be given as teletherapy (also known as external beam radiotherapy), when a beam of radiation is aimed at the area to be treated from a machine located away from the patient.
Other forms of radiotherapy are high or low-dose brachytherapy, which involves a radioactive source being placed on or in a tumour.
Dose:
The amount of radiation used in photon radiation therapy is measured in gray (Gy), and varies depending on the type and stage of cancer being treated. For curative cases, the typical dose for a solid epithelial tumor ranges from 60 to 80 Gy, while lymphomas are treated with 20 to 40 Gy.
Preventative (adjuvant) doses are typically around 45 – 60 Gy in 1.8 – 2 Gy fractions (for Breast, Head, and Neck cancers.) Many other factors are considered by radiation oncologists when selecting a dose, including whether the patient is receiving chemotherapy, patient comorbidities, whether radiation therapy is being administered before or after surgery, and the degree of success of surgery.
Delivery parameters of a prescribed dose are determined during treatment planning (part of dosimetry). Treatment planning is generally performed on dedicated computers using specialized treatment planning software. Depending on the radiation delivery method, several angles or sources may be used to sum to the total necessary dose. The planner will try to design a plan that delivers a uniform prescription dose to the tumor and minimizes dose to surrounding healthy tissues.
Treatment planning
All patients who are to have radiotherapy need individually tailored treatment so it is given accurately. A lot of information is needed so the doctor can target the tumour while minimising damage to the healthy tissue. This is called treatment planning and there are a number of ways of doing this.
Simulator planning is done using a specialised x-ray machine that can do the same things as the treatment machines except deliver treatment. The simulator allows the doctor to carefully look at the area that needs treatment and plan it precisely. During the planning, the radiographer will draw some marks on the skin using a pen; when the doctor and radiographer are happy they have an accurate plan, the radiographer may need to make two to three permanent marks called tattoos. These tattoos are the size of a pinhead and are used to ensure the radiotherapy is given to exactly the right place.
ACQSIM planning is done using a scanner. Some patients may need to have an intravenous injection before the scan to show up the area to be treated better. The scan usually takes about 15 minutes and the information from the scan is used to produce a treatment map. Sometimes it’s necessary to take some x-rays and measurements to check the treatment map and this is done on the simulator.
What radiotherapy involves
When radiotherapy treatment is being given by external beam, it’s important the patient is in exactly the same position each time. The radiographers will often use pillows and wedges to make sure the patient is comfortable and in the correct position.
Patients having radiotherapy to the head or neck area may need to have a mould made to keep them in the right position. Moulds are made from clear Perspex after a plaster cast has been made of the head and neck. Once the Perspex mould has been made, the radiotherapy is planned while the patient is wearing the mould and marks are drawn on the mask instead of the skin.
Once the radiographers are happy that the patient is in the correct position they will leave the room to switch the treatment machine on. When the machine is on it makes a buzzing noise. The radiographers watch closely on a television screen. Treatment only lasts a few minutes and does not hurt.
Side effect of radiotherapy
Side effects are different depending on the part of the body being treated. Most side effects are temporary but some may continue for weeks or months after treatment is finished. They include:
•Hair loss (alopecia)
•Cerebral oedema (excess fluid accumulating in the brain) can cause changes in mental state, restlessness, irritability, impaired pupil reactions, headache, increase in blood pressure, decrease in pulse and respiration, and nausea
•Dry or sore mouth or throat, changes in taste sensation, skin thickening
•Inflammation of the gullet, indigestion, nausea, lung inflammation
•Nausea and vomiting, diarrhoea, cystitis
•Sexual dysfunction. In males treatment of the abdomen area can cause impotence, sterility. In females it can cause sterility, loss of sexual desire. Irradiation of the pelvis may cause tightening of the vagina, loss of vaginal lubrication, inflammation or ulceration of the vagina. Some women may find intercourse painful
•Treatment of red bone marrow may cause infection and impaired healing, anaemia, increased tiredness, bruising and bleeding
As well as treating cancer the radiotherapy temporarily damages the outer layers of skin. During treatment the skin cannot repair itself as it normally would and it can become sore. But once treatment has finished the skin generally recovers quite quickly – usually within a month. The level of reaction can depend on your skin type, the type and number of treatments you have, and how you would normally react to the sun.
Skin side effects usually happen later on in the course of radiotherapy treatment or sometimes a few weeks after treatment has finished. Many patients do not have any skin changes at all. Skin care advice will be given to the patients by the staff treating them.
A common side effect of radiotherapy is tiredness and fatigue, which often prevents patients from doing normal everyday activities. Fatigue and tiredness are normal results of having radiotherapy and begin in the first week of treatment, reaching a peak after two weeks of treatment and gradually disappearing a few weeks after treatment has finished.
Radiation therapy accidents:
There are rigorous procedures in place to minimise the risk of accidental overexposure of radiation therapy to patients. However, mistakes do occasionally occur; for example, the radiation therapy machine Therac-25 was responsible for at least six accidents between 1985 and 1987, where patients were given up to one hundred times the intended dose; two people were killed directly by the radiation overdoses. From 2005 to 2010, a hospital in Missouri overexposed 76 patients (most with brain cancer) during a five-year period because new radiation equipment had been set up incorrectly. Although medical errors are exceptionally rare, radiation oncologists, medical physicists and other members of the radiation therapy treatment team are working to eliminate them. ASTRO has launched a safety initiative called Target Safely that, among other things, aims to record errors nationwide so that doctors can learn from each and every mistake and prevent them from happening. ASTRO also publishes a list of questions for patients to ask their doctors about radiation safety to ensure every treatment is as safe as possible.
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
Resources:
http://en.wikipedia.org/wiki/Radiation_therapy
http://www.bbc.co.uk/health/physical_health/conditions/in_depth/cancer/carecancer_radio.shtml
http://www.allvitalpoints.com/2010/how-radiotherapy-is-performed/
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