How does radiotherapy work?
Radiotherapy works by destroying cancer cells in the area that’s being treated. Normal, healthy cells can also be damaged by radiotherapy, which may cause side effects. Cancer cells cannot repair themselves after radiotherapy, but normal cells usually can.
Radiotherapy can be given for different reasons.
Curative Treatment – This is when doctors give radiotherapy to try and destroy a tumour and cure the cancer. This can often be given with other treatments, such as surgery or chemotherapy.
Palliative treatment – A doctor may give radiotherapy to help relieve the symptoms when it’s not possible to cure the cancer.
The type of radiotherapy given will depend on the type of cancer, where it is located and an individual’s situation.
What types of radiotherapy are there?
There are 2 types of radiotherapy – internal and external.
External radiotherapy is delivered outside the body. This involves directing high-energy radiation beams at the area being targeted within the body using various different radiotherapy machines (most people will have this type of radiotherapy).
External beam radiotherapy is usually carried out as an outpatient procedure which does not require a stay in hospital. However there maybe circumstances if treatments are being given in combination (radiotherapy, surgery and chemo) that becoming an inpatient maybe necessary. Especially if patients feel unwell and need some respite.
There are various different types of external beam radiotherapy but in the majority of cases a patient will be positioned on the treatment couch by the therapy radiographers and a radiotherapy machine will be used to direct high-energy radiation beams at the area being treated.
The treatment will be completely painless and each session should only take a few minutes. Patients will need to keep as still as possible throughout the treatment. Some treatment techniques may involve special instructions but these will be fully explained before any treatment is delivered. When the radiation is being delivered patients will be left alone in the treatment room, radiographers will be operating the radiotherapy machine from outside. Patients are constantly monitored via CCTV by the radiographers and can be heard at all times via an intercom. The treatment delivery itself only takes a matter of minutes so the time spent alone in the room is very short.
External Beam radiotherapy
There are different types of radiation beam that can be used and different techniques \ methods of treatment delivery.
Below are some commonly used descriptions….
Intensity-Modulated Radiation Therapy (IMRT) shapes the radiotherapy beams allowing different doses to be given to different parts of the area needing treatment. This gives us control of the radiation enabling us to avoid or minimise exposure to surrounding healthy tissue. This is particularly effective when dealing with cancers that are close to vital organs or structures within the body. IMRT can be used to treat any part of the body
Stereotactic Body Radiation Therapy (SBRT) also called SABR is a type of therapy where a few very high doses of radiation are delivered to relatively small, well-defined tumours. SBRT is used to treat small, isolated tumours that lie outside the brain. SBRT treatment allows multiple radiation beams to be directed at any part of the body from any direction to deliver a high radiation dose to the tumour and, at the same time, limit damage to healthy tissue. Many doctors refer to SBRT systems by their brand names such as CyberKnife (a sophisticated robotic external beam radiotherapy system).
Image-guided radiation therapy (IGRT) describes the use of a variety of advanced imaging modalities throughout the course of radiotherapy to accurately identify and localise the treatment area before the radiation is delivered. Many different modalities are used and this will depend on what is available in the radiotherapy department and the type of treatment machines that are being used. The images taken are used not only to verify the treatment positioning but can also identify changes in a tumour’s size and location to enable adjustments to be made during treatment such as the position of the patient or the planned radiation dose. IGRT is incorporated into the delivery of IMRT and SBRT radiotherapy regimes
Electron Therapy or Electron Beam Therapy (EBT) is a type of external beam radiotherapy that uses electrons instead of photons (photons are the most commonly used type of radiation therapy). Electrons do not penetrate the body as deeply as photons and are therefore used to treat more superficial (closer to the skin) areas, this spares the deeper tissues not requiring treatment
Proton Therapy or Proton Beam Therapy is a type of external beam therapy that uses protons to deliver radiation dose to the body. Because of how protons react with the tissues of the body it can be directed at a tumour potentially at a more precise depth than photons. In theory the use of protons can reduce the exposure of radiation to normal tissues, but the interaction this beam has within the moving body is still being investigated. Currently the only facility in the UK that offers this type of therapy is Clatterbridge Centre for Cancer NHS Foundation Trust, in Wirral. They only offer treatment for rare cancers of the eye.
Internal radiotherapy involves having radioactive material placed inside the body. These can be either radioactive implants (such as metal wires, seeds, or tubes placed inside the body, within or close to a tumour) or radioactive liquids (given either as a drink, capsule or injection)
Brachytherapy (internal implants) is when radioactive material is inserted directly into and around the affected area (metal wires, seeds or tubes). A relatively high dose of radiation is given to the tumour \ target area whilst healthy surrounding tissue only gets a very small amount of radiation. In some types of cancer these implants may be left in the body permanently. This type of therapy is usually given on an outpatient basis but can sometimes involve staying in hospital for a few days until the radioactive source has been removed.
Radioisotope or Radionuclide therapy delivers radiation directly into the cancer cells via a capsule, drink or injection into a vein. Cancer cells specifically absorb the radioactive substance more than normal, healthy cells which means they receive a higher dose of radiation. The radioactive part of the liquid is called an isotope. It may be attached to another substance, which is designed to take the isotope into the tumour. There are different types of radioisotope used for different types of cancers e.g. phosphorous, radium, strontium and iodine. For this type of treatment, it may be necessary to stay in hospital for a few days until most of the radioactivity has disappeared from your body. Please note these can be used for non-cancerous therapies also.
SIRT (also known as radio-embolisation) is a special type of internal radiotherapy that uses high doses of radiation to target liver tumours inside the body. It delivers much higher doses of radiation over much longer periods of time than would be possible with external beam radiation and works by delivering microspheres to the liver which lodge themselves in the very small blood vessels in and around the liver tumours giving off high doses of radiation. This radiation will affect only a small area, meaning the liver tumour is directly targeted while doing little damage to the surrounding healthy liver. The radiation effect on the tumour lasts for about two weeks, after which only 3% of the initial useful radiation remains. After one month it has all gone, but the effects of the radiotherapy on the cancer last much longer.