Radiotherapy For Cancer: Radiation that heal
Radiation therapy (radiotherapy) in addition to the operation and chemotherapy is one of the central pillars of cancer therapy. Every cancer patients use radiotherapy in the course of his illness. Unlike chemotherapy in which drug are acting throughout the body ( “systemic”), the radiation treatment is a purely local measure in which the tumoricidal effect occurs only within the irradiation field.
Radiation therapy may be used in combination with chemotherapy (radiochemotherapy) after (adjuvant) or before (neoadjuvant) operation as the sole method of treatment. Some cancers, such as localized laryngeal cancer or prostate cancer can be cured by a sole radiotherapy. Moreover, a radiation therapy can be used in cancer treatment to alleviate or prevent symptoms.
How does radiation therapy work?
In the radiotherapy, the cancer cells are destroyed using ionizing radiation or particle radiation. The radiation damages the genetic material of cells, so that cell division stops. The tumors may reduced in size or even disappear.
The cytotoxic effect of radiation therapy is not specific, healthy cells are also affected. However, depending on the degree of damage, the cell’s own repair systems repair the damage to the genetic material.
The doctor selects the radiation dose based on the radio-sensitivity of the tumor. The dose of 40 to 70 Gray (Gy) is used to achieved the cure, this unit is to be after the name of British physicist and father of radiobiology, Louis Harold Gray. For tumor destruction it is necessary to divide total into fractions of 1.8 to 2 Gy . This ensures good compatibility is achieved and reduces the risk of permanent damage and late complications. However, the reparability of the healthy tissue remains the limiting factor for radiation therapy, which is to serve the healing. New techniques of precision radiation permit accurate localization to the tumor tissue. Thus, healthy tissue can be better protected. With such techniques, a so-called hypofractionated radiation is possible; ie, the necessary radiation dose is administered in a few fractions. On the repairability of the healthy tissue less consideration has to be taken.
The extreme form of precision irradiation is the so-called Radio surgery where the patient receives a high dose in one day. When a radio-surgery is done high number of tumor cells are dies with a blow and charged the body through a large number of cellular debris and decomposing products.
Palliative radiation therapy is used to alleviate pain and other symptoms of tumor diseases. Here, the tumors or metastases are specifically irradiated which cause discomfort. This is often done in a few sessions and use high single doses (hypofractionation) to maintain the physical and time burden of patients low. Typical regulations are: 10 x 3 Gy; 5 x 4 Gy or 1 x 8 Gy.
Palliative radiotherapy is very effective. It relieves pain or reduced tumor swelling.
Which radiation treatments are available?
The substance may cause radiation from the outside with linear accelerators. There is also radiotherapeutic treatments radionuclide, which are carried out in the context of nuclear medicine.
Radiation from outside
the irradiation takes place from the outside through the skin (percutaneous). The devices are mostly linear accelerator. Patients lie lounger under the irradiation device and they cannot move because they fixed. In most cases, percutaneous radiotherapy carried out fractionally, ie. At several meetings.
The various irradiation methods through the skin are not equally suitable for all types of cancer:
Conventional Radiation Therapy: use of conventional “flat” ( not three-dimensional) e.g. after breast-conserving surgery for breast cancer..
Conformational Irradiation (3D Radiation): The radiation field is possible precisely adjusted using screens and filters respectively to the tumor shape and size to protect the surrounding tissue. The Conformational Irradiation can be used against tumors that are close to vital organs or structures that may not be damaged.
Intensity Modulated Radiation Therapy (IMRT): Development of 3D radiation therapy, in which the beam direction is continuously changed so that the beams run permanently by the tumor, but at the same time, varies the affect on healthy tissue. The radiation intensity within the tumor can be changed. IMRT can be use in prostate cancer, brain tumors, tumors in the head and neck (mouth, throat, neck), tumors of the digestive tract and in the genital area.
Stereotactic Radiotherapy ( “Gamma Knife, Cyberknife, Radiosurgery”): Here, the treatment beams from different angles of incidence meet precisely to the tumor, the patient is either fixed or its spontaneous movements or breathing movements are automatically compensated. In healthy tissue meets only a small dose of radiation along the Single beam tracks, so that the tumor can be irradiated with high doses of energy itself. The irradiation is thus very precise , comparable to a surgical procedure, which is why this type of irradiation is referred to as radiosurgery . Stereotactic radiation is suitable for brain tumors, tumors in the head and neck area as well as tumors and metastases in the lungs, liver, prostate and spine.
Ion Therapy (Proton, Heavy Ion Radiation): Irradiation with protons or other heavy ions, which only release their radiation energy when they are slowed down and it is happen when they penetrating the tissue and achieve a lower speed. By varying the beam energy, the depth of the dose distribution can be controlled. This allows a better focusing of the radiation on the tumor tissue and sparing the healthy tissue. The ion therapy is well suited for the irradiation of such tumors, which are more resistant to conventional radiotherapy, e.g. in tumors of the skull base as chondromata (benign cartilage-forming tumors), chondrosarcoma (malignant bone tumor) and meningiomas (usually benign tumors of the meninges ) or tumors of the salivary glands.
Intraoperative Radiotherapy (IORT): The tumor is irradiated directly during surgery through the open body cavity. The surgeons have removed tumor mass and expose the tissue to be taken, so that the so-called “tumor bed” can be irradiated in the presence of a surgeon and under radiation oncologists vision. The IORT is suitable for irradiation in the abdominal area, because as surrounding organs can be well protected. Also in the context of breast-conserving treatment of breast cancer, intra-operative irradiation are applied in order to reduce the duration of irradiation through the skin.
The radiation from the outside can be carried out in combination with chemotherapy as chemo-radiation. Here, the chemotherapies is used to increase the radio-sensitivity of the tumor tissue, thereby the efficiency of the radiation increases. Not all chemotherapy drugs are suitable for simultaneous application with ionizing radiation. Treatment with radio-chemotherapy requires a lot of experience and close coordination of both therapies.
Radiation From The Inside: Brachytherapy
In brachytherapy, radiation source is placed directly on the tumor or in the exact location in the body where the tumor was located before surgery. The radiation has only a low range of a few millimeters The tumor tissue can be irradiated with this method with a high dose, without the healthy tissue would be greatly damaged to. Brachytherapy is good with cervical cancer , with prostate cancer , sarcomas or head and neck cancer .
A special form of radiation from the inside is the so-called afterloading. This strong source of radiation is use for a short period. Radiation sources are inserted through hollow tubes or hollow needles through the and are removed at the end of therapy. The Afterloading. is used in colorectal cancer ( rectum ), when the sphincter should be preserved, in cervical cancer and vaginal cancer .
Nuclear Medicine Applications
In a nuclear medicine, radioactive substances are used: Most are beta emitters. They are incorporated in the form of medicines into the body, e.g., By spraying. Through metabolism the radioactive substances reach into the affected organ, destroying the diseased cells and disintegrate within hours or days. Another possibility is this type of radiotherapy e.g. in bone metastases. The radio-nuclides accumulate preferentially in the metastases and can destroy them.
Side Effects of Radiotherapy:
Side effects during radiation therapy appear generally local, organ-based and temporary. Acute symptoms after radiotherapy in head and neck area are mucosal inflammation in the mouth or in the esophagus and skin redness may occur at the irradiated areas of the body. Nausea, vomiting or diarrhea may be side effects of irradiation of the abdominal region. Brain irradiation can cause hair loss. Radiation therapy may also be the cause of fatigue, fever and loss of appetite, but these symptoms are usually temporary. Due to late reactions or induration of subcutaneous fat or skin lesions may occur.
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