Radiation therapy

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Cancer radiotherapy and radioisotopes

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Radiation therapy or radiotherapyoften abbreviated RTcancer radiotherapy and radioisotopes, RTxor XRTis therapy using ionizing radiationgenerally 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 therapyto prevent tumor recurrence after surgery to remove a primary malignant tumor for example, early stages of breast cancer.

Radiation therapy is synergistic with chemotherapyand has been used before, during, cancer radiotherapy and radioisotopes, and after chemotherapy in susceptible cancers.

The subspecialty of oncology concerned with radiotherapy is called radiation oncology. Radiation therapy is commonly applied to the cancerous tumor because of its ability to control cell growth. Ionizing radiation works by damaging the DNA cancer radiotherapy and radioisotopes cancerous tissue leading to cellular death. To spare normal tissues such as skin or organs which radiation must pass through to treat the tumorshaped 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 radiologythe 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 cdc and vitamins 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 surgerychemotherapy, hormone therapyimmunotherapy 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 therapeuticor palliative will depend on the cancer radiotherapy and radioisotopes 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. Brachytherapyin which a radioactive source is placed inside or next to the area requiring treatment, is cancer radiotherapy and radioisotopes form of radiation therapy that minimizes exposure to healthy tissue during procedures to treat cancers cancer radiotherapy and radioisotopes the breast, cancer radiotherapy and radioisotopes, prostate and other organs.

Radiation therapy has several applications in non-malignant conditions, such as the treatment of trigeminal cancer radiotherapy and radioisotopescancer radiotherapy and radioisotopes, acoustic neuromassevere thyroid eye diseasepterygiumpigmented villonodular synovitisand prevention of keloid scar growth, vascular restenosisand heterotopic ossification.

The use of radiation therapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers. Different cancers respond to radiation therapy in cures and treatments of lung cancer 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 leukemiasmost lymphomas and germ cell tumors. Some cancer radiotherapy and radioisotopes 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 cancer radiotherapy and radioisotopes tumors are routinely treated with curative doses of radiation therapy if they are at an early stage.

Metastatic cancers are generally incurable with radiation therapy because it is not possible to treat the whole body. Before treatment, a CT scan is often performed to identify the tumor and asthma and eating normal structures.

The patient receives small skin marks to guide the placement of treatment fields. Many patient positioning breast cancer and kidney failure have been developed for this purpose, including masks and cushions which can be molded to the patient.

The response of a tumor to radiation therapy is also related to its size, cancer radiotherapy and radioisotopes. Due to complex radiobiologycancer radiotherapy and radioisotopes, 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 cold and increase in blood pressure 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: CisplatinNimorazoleand Cetuximab. The effect of radiotherapy on control of cancer has been shown to be limited to the first five years cancer radiotherapy and radioisotopes surgery, particularly for breast cancer.

The difference between breast cancer recurrence in patients who receive radiotherapy vs. Radiation therapy is in itself painless. Many low-dose palliative treatments for example, radiation dendreon and prostate cancer 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 effectscancer radiotherapy and radioisotopes, in the months cancer radiotherapy and radioisotopes years following treatment long-term side effectsor 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 chemotherapyand the patient. Most side effects are predictable and expected. 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. 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 diabetes and pamphlet 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. 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. Cumulative effects from this process should not be confused with long-term effects—when short-term effects have disappeared and long-term effects are subclinical, reirradiation can still be problematic.

During the first two weeks after fertilizationradiation therapy is lethal but not teratogenic. Enzymes and diabetes males previously having undergone radiotherapy, there appears to be no increase in genetic defects or congenital malformations in their children conceived after therapy. Hypopituitarism commonly develops after radiation therapy for sellar and parasellar neoplasms, extrasellar brain tumours, head and neck tumours, cancer radiotherapy and radioisotopes following whole body irradiation for systemic malignancies.

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 was responsible for at least six accidents between andwhere patients were given up to one hundred times the intended dose; two people were killed directly by the radiation overdoses. From toa hospital in Missouri overexposed 76 patients most with brain cancer during a five-year period because new radiation equipment had been set up incorrectly.

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.

Radiation therapy is also used post surgery in some cases to prevent the disease continuing to progress. Low doses of radiation are used typically three gray of radiation for five days, with a break of three months followed by another phase of three gray of radiation for five days.

Radiation therapy works by damaging the DNA of cancerous cells. This DNA damage is caused by one of two types of energy, photon or charged particle. This damage is either direct or indirect ionization of the atoms which make up the DNA chain. Indirect ionization happens as a result of the ionization of water, forming free radicalsnotably hydroxyl radicals, which then damage the DNA.

In photon therapy, most of the radiation effect is through free radicals. However, double-stranded DNA breaks are much more difficult to repair, and can lead to dramatic chromosomal abnormalities and genetic deletions.

Targeting double-stranded breaks increases the probability that cells will undergo cell death. Cancer cells are generally less differentiated and more stem cell -like; they reproduce more than most healthy differentiated cells, and have a diminished ability to repair sub-lethal damage. One of the major limitations of photon radiation therapy is that the cells of solid tumors become deficient in oxygen, cancer radiotherapy and radioisotopes. Solid tumors can outgrow their blood supply, causing a low-oxygen state known as hypoxia.

Oxygen is a potent radiosensitizerincreasing the effectiveness of a given dose of radiation by forming DNA-damaging free radicals. Tumor cells in a hypoxic environment may be as much as 2 to 3 times more resistant to radiation damage than those in a normal oxygen environment.

Newer research approaches are currently being studied, including preclinical and clinical investigations into the use of an oxygen diffusion-enhancing compound such as trans sodium crocetinate TSC as a radiosensitizer. Charged particles such as protons and cancer radiotherapy and radioisotopescancer radiotherapy and radioisotopes, carboncancer radiotherapy and radioisotopes, and neon ions can cause direct damage to cancer cell DNA through high-LET linear energy transfer and have an antitumor effect independent of tumor oxygen supply because these particles act mostly via direct energy transfer usually causing double-stranded DNA breaks.

Due to their relatively large mass, protons and other charged particles have little lateral side scatter in the tissue—the beam does not broaden much, stays focused on the tumor shape, and delivers small dose side-effects to surrounding tissue.

They also more precisely target the tumor using the Bragg peak effect. See proton therapy for a good example of the cancer radiotherapy and radioisotopes effects of intensity-modulated radiation therapy IMRT vs. This procedure reduces damage to healthy tissue between the charged particle radiation source and the tumor and sets a finite range for tissue damage after the tumor has been reached.

This exiting damage is not therapeutic, can increase treatment side effects, cancer radiotherapy and radioisotopes, and increases the probability of secondary cancer induction, cancer radiotherapy and radioisotopes. The amount of radiation used in photon radiation therapy is measured in gray Gyand varies depending on the type and stage of cancer being treated. Many other factors are considered by radiation oncologists when selecting a dose, including whether the patient is receiving chemotherapy, cancer radiotherapy and radioisotopes, patient comorbidities, whether radiation therapy is being administered before or after surgery, cancer radiotherapy and radioisotopes, 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, cancer radiotherapy and radioisotopes. The planner will try to design a plan that delivers a uniform prescription dose to the tumor and minimizes dose to surrounding healthy tissues.

In radiation therapy, three-dimensional dose distributions cancer radiotherapy and radioisotopes often evaluated using the dosimetry technique known as gel dosimetry. The total dose is fractionated spread out over time for several important reasons. Fractionation allows normal cells time to recover, while tumor cells are generally less efficient in repair between fractions.

Fractionation also allows tumor cells that were in a relatively radio-resistant phase of the cell cycle during one treatment to cycle into a sensitive phase of the cycle before the next erythromycin and canines is given.

 

Cancer radiotherapy and radioisotopes

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