What is radiotherapy?
Radiotherapy is a way of treating cancer or the symptoms of cancer using energy in the form of radiation. The type of radiotherapy will depend on the location and type of cancer.
What is radiation?
Radiation is a way of transferring energy that includes the more everyday examples of visible light, radio waves and sound. The radiation that is used for radiotherapy transfers a lot of energy, so much so that it can damage the molecules that make up living tissue when it is absorbed. This type of radiation is called ionising radiation. It can be given in the form of photon therapy – a very high energy form of light such as X-rays or gamma rays. Photons are “light particles” and are what scientists use to help explain how light behaves. Radiotherapy can also be given as high energy beams of particles that come from atoms. These are the electron beam and proton beam therapies.
How does radiation treat cancer?
When radiation enters body tissues the energy it carries is transferred to the molecules that make up our cells. The amount of energy delivered is high enough to damage these molecules. One of the most important molecules in the body is DNA. DNA holds the instructions that control everything that a cell makes and does. When a cell divides it makes an identical copy of itself, including its DNA. If the DNA has been sufficiently damaged by radiation the copying doesn’t work, the cell can’t divide and will eventually die.
Cancer cells are very sensitive to radiation because they divide frequently, DNA is more easily damaged during division, and their DNA has already been damaged by the processes that caused the cancer in the first place.
Most normal cells divide less often and are better at repairing radiation damage, but can still be damaged if radiation passes through them. This is what causes some of the side effects of radiotherapy such as skin damage, fatigue and nausea.
When is radiotherapy used?
Radiotherapy could be used at all stages of cancer treatment depending on the type, stage and location of the cancer. It can be used to reduce, or even cure small or early tumours, possibly with additional chemotherapy. It can be used before surgery to reduce the size of a tumour or to remove any remaining cells afterwards. It can help prevent or treat any cancer that has spread from the original site. Radiotherapy is also very useful for treating the symptoms of advanced cancer, such as bone pain or difficulty breathing, by reducing the size of tumours that are causing problems.
What types of radiotherapy are there?
In short, external beams or a source placed in the body (brachytherapy) or taken in by mouth or through a vein (systemically).
In external beam therapy, beams of X-rays, gamma rays, electrons or protons are directed at the tumour from many different angles. Some damage can occur to healthy tissue each time, but by sending the beam from many different angles the healthy tissue is much less affected than the tumour, which is always in its path. There are several different techniques that use different types of imaging (CT scans, MRI scans etc)to make sure the tumour is precisely targeted.
Brachytherapy is putting radioactive beads, pellets or ribbons into a tumour or a place where a tumour has been removed. This means that the radiation does not have to travel through healthy tissue before getting to the tumour. Radiation is released in all directions from the radioactive source. The treatment can be removed after a short time, or left in place.
The most well known type of systemic radiotherapy is for thyroid cancer. Your thyroid is a gland in your neck that makes the hormone thyroxine using the element iodine. Most of the iodine from our diet ends up there. People with thyroid cancer are given radioactive iodine which only targets thyroid cells wherever they are and destroys them.
More recent treatments have used radioactive substances attached to antibodies. Antibodies are molecules that are normally made by the immune system and stick to and mark invading bacteria or viruses for destruction. They can also be made against cancer cells and large amounts of identical antibodies produced (monoclonal means a copy from one original). By adding a radioactive part to these antibodies, radiation can be sent directly to cancer cells.
How safe and effective is radiotherapy?
We tend to think of radiation as something that causes cancer. People exposed to radiation from nuclear bombs or exposure through their work (Marie Curie is a famous example) or accidents such as the Chernobyl disaster developed cancer. This was because the radiation damaged their normal DNA and created changes that allowed cells to divide uncontrollably. In these examples the amount, or dose of radiation was very high, or over a long time and to the whole body.
In radiotherapy the dose is carefully worked out to be as low as possible and imaging techniques make sure it is only delivered to the tumour and the smallest possible area of normal tissue. There is still a small risk of it causing a second cancer, but this is balanced against the need to treat the original cancer.
Radiotherapy is a very effective treatment for cancer – around 40% of all cases of cured disease involve radiotherapy and it can have a big impact on easing symptoms where a cure is not possible.
What new developments are there?
There have been a lot of news stories about the development of proton beam therapies for cancer, especially breast cancer. Protons are particles that make up atoms and when fired at high energy into the body, they don’t travel as far as X-rays, either into the body, or beyond the tumour. This means they have the potential to be less damaging than conventional beam therapy. A recent study has looked at using proton beam therapy for breast cancer as normal radiotherapy potentially damages the heart as it is close to the treatment site.
How does membership of RareCan help?
Researchers are constantly developing new radiotherapy treatments or finding better ways of combining radiotherapy with other treatments. In order for these to become accepted as a valid method to treat rare cancers it is essential for them to work with sufficient patients with a particular cancer that they can show their treatment works. By being a member of RareCan