radiation therapy radiation therapy radiation therapy or radiotherapy, often abbreviated rt, rtx, or xrt, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. radiation therapy may be curative in a number of types of cancer if they are localized to one area of the body. it may also be used as part of adjuvant therapy, to prevent tumor recurrence after surgery to remove a primary malignant tumor (for example, early stages of breast cancer). radiation therapy is synergistic with chemotherapy, and has been used before, during, and after chemotherapy in susceptible cancers. the subspecialty of oncology concerned with radiotherapy is called radiation oncology. a physician who practices in this subspecialty is a radiation oncologist. "radiation (medicine)" redirects here. not to be confused with radiation (pain) or radiology. radiation therapyradiation therapy of the pelvis, using a varian clinac ix linear accelerator. lasers and a mould under the legs are used to determine exact position.icd-10-pcsdicd-9-cm92.2-92.3meshd011878ops-301 code8–52medlineplus001918 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 cancerous tissue leading to cellular death. to spare normal tissues (such as skin or organs which radiation must pass through 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 the 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 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 radioactive 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, acoustic neuromas, 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. medical uses radiation therapy for a patient with a diffuse intrinsic pontine glioma, with radiation dose color-coded different cancers respond to radiation therapy in different ways. the response of a cancer to radiation is described by its radiosensitivity. highly radiosensitive cancer cells are rapidly killed by modest doses of radiation. these include leukemias, most lymphomas and germ cell tumors. the majority of epithelial cancers are only moderately radiosensitive, and require a significantly higher dose of radiation (60-70 gy) to achieve a radical cure. some types of cancer are notably radioresistant, that is, much higher doses are required to produce a radical cure than may be safe in clinical practice. renal cell cancer and melanoma are generally considered to be radioresistant but radiation therapy is still a palliative option for many patients with metastatic melanoma. combining radiation therapy with immunotherapy is an active area of investigation and has shown some promise for melanoma and other cancers. it is important to distinguish the radiosensitivity of a particular tumor, which to some extent is a laboratory measure, from the radiation "curability" of a cancer in actual clinical practice. for example, leukemias are not generally curable with radiation therapy, because they are disseminated through the body. lymphoma may be radically curable if it is localised to one area of the body. similarly, many of the common, moderately radioresponsive tumors are routinely treated with curative doses of radiation therapy if they are at an early stage. for example, non-melanoma skin cancer, head and neck cancer, breast cancer, non-small cell lung cancer, cervical cancer, anal cancer, and prostate cancer. with the exception of oligometastatic disease, metastatic cancers are incurable with radiation therapy because it is not possible to treat the whole body. modern radiation therapy relies on a ct scan to identify the tumor and surrounding normal structures and to perform dose calculations for the creation of a complex radiation treatment plan. the patient receives small skin marks to guide the placement of treatment fields. patient positioning is crucial at this stage as the patient will have to be placed in an identical position during each treatment. many patient positioning devices have been developed for this purpose, including masks and cushions which can be molded to the patient. image-guided radiation therapy is a method that uses imaging to correct for positional errors of each treatment session. the response of a tumor to radiation therapy is also related to its size. due to complex radiobiology, very large tumors respond less well to radiation than smaller tumors or microscopic disease. various strategies are used to overcome this effect. the most common technique is surgical resection prior to radiation therapy. this is most commonly seen in the treatment of breast cancer with wide local excision or mastectomy followed by adjuvant radiation therapy. another method is to shrink the tumor with neoadjuvant chemotherapy prior to radical radiation therapy. a third technique is to enhance the radiosensitivity of the cancer by giving certain drugs during a course of radiation therapy. examples of radiosensitizing drugs include cisplatin, nimorazole, and cetuximab. the impact of radiotherapy varies between different types of cancer and different groups. for example, for breast cancer after breast-conserving surgery, radiotherapy has been found to halve the rate at which the disease recurs. in pancreatic cancer, radiotherapy has increased survival times for inoperable tumors. side effects radiation therapy is in itself painless. many low-dose palliative treatments (for example, radiation therapy to bony metastases) cause minimal or no side effects, although short-term pain flare-up can be experienced in the days following treatment due to oedema compressing nerves in the treated area. higher doses can cause varying side effects during treatment (acute side effects), in the months or years following treatment (long-term side effects), or after re-treatment (cumulative side effects). the nature, severity, and longevity of side effects depends on the organs that receive the radiation, the treatment itself (type of radiation, dose, fractionation, concurrent chemotherapy), and the patient. most side effects are predictable and expected. side effects from radiation are usually limited to the area of the patient's body that is under treatment. side effects are dose- dependent; for example higher doses of head and neck radiation can be associated with cardiovascular complications, thyroid dysfunction, and pituitary axis dysfunction. modern radiation therapy aims to reduce side effects to a minimum and to help the patient understand and deal with side effects that are unavoidable. the main side effects reported are fatigue and skin irritation, like a mild to moderate sun burn. the fatigue often sets in during the middle of a course of treatment and can last for weeks after treatment ends. the irritated skin will heal, but may not be as elastic as it was before. acute side effects nausea and vomiting this is not a general side effect of radiation therapy, and mechanistically is associated only with treatment of the stomach or abdomen (which commonly react a few hours after treatment), or with radiation therapy to certain nausea-producing structures in the head during treatment of certain head and neck tumors, most commonly the vestibules of the inner ears. as with any distressing treatment, some patients vomit immediately during radiotherapy, or even in anticipation of it, but this is considered a psychological response. nausea for any reason can be treated with antiemetics. damage to the epithelial surfaces epithelial surfaces may sustain damage from radiation therapy. depending on the area being treated, this may include the skin, oral mucosa, pharyngeal, bowel mucosa and ureter. the rates of onset of damage and recovery from it depend upon the turnover rate of epithelial cells. typically the skin starts to become pink and sore several weeks into treatment. the reaction may become more severe during the treatment and for up to about one week following the end of radiation therapy, and the skin may break down. although this moist desquamation is uncomfortable, recovery is usually 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. mouth, throat and stomach sores 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/food supplements. the esophagus can also become sore if it is treated directly, or if, as commonly occurs, it receives a dose of collateral radiation during treatment of lung cancer. when treating liver malignancies and metastases, it is possible for collateral radiation to cause gastric, stomach or duodenal ulcers this collateral radiation is commonly caused by non-targeted delivery (reflux) of the radioactive agents being infused. methods, techniques and devices are available to lower the occurrence of this type of adverse side effect. intestinal discomfort the lower bowel may be treated directly with radiation (treatment of rectal or anal cancer) or be exposed by radiation therapy to other pelvic structures (prostate, bladder, female genital tract). typical symptoms are soreness, diarrhoea, and nausea. nutritional interventions may be able to help with diarrhoea associated with radiotherapy. studies in people having pelvic radiotherapy as part of anticancer treatment for a primary pelvic cancer found that changes in dietary fat, fibre and lactose during radiotherapy reduced diarrhoea at the end of treatment. swelling as part of the general inflammation that occurs, swelling of soft tissues may cause problems during radiation therapy. this is a concern during treatment of brain tumors and brain metastases, especially where there is pre-existing raised intracranial pressure or where the tumor is causing near-total obstruction of a lumen (e.g., trachea or main bronchus). surgical intervention may be considered prior to treatment with radiation. if surgery is deemed unnecessary or inappropriate, the patient may receive steroids during radiation therapy to reduce swelling. infertility the gonads (ovaries and testicles) are very sensitive to radiation. they may be unable to produce gametes following direct exposure to most normal treatment doses of radiation. treatment planning for all body sites is designed to minimize, if not completely exclude dose to the gonads if they are not the primary area of treatment. late side effects late side effects occur months to years after treatment and are generally limited to the area that has been treated. they are often due to damage of blood vessels and connective tissue cells. many late effects are reduced by fractionating treatment into smaller parts. fibrosis tissues which have been irradiated tend to become less elastic over time due to a diffuse scarring process. epilation epilation (hair loss) may occur on any hair bearing skin with doses above 1 gy. it only occurs within the radiation field/s. hair loss may be permanent with a single dose of 10 gy, but if the dose is