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Radiotherapy

radiotherapy

Radiotherapy is a along with surgery and chemotherapy to treat cancer. High-energy beams of radiation are focused on cancerous tissue. This kills cancer cells or stops cancer cells from multiplying. It is sometimes also called as radiation therapy.

Surgery is done to remove a tumour but, sometimes a course of radiotherapy is also given after surgery, to kill any cancer cells remaining after surgery. Unless treated, these remaining cancer cells may lead to a recurrence of the tumour at a later time. Radiotherapy given after surgery is called adjuvant radiotherapy.Radiotherapy can also be given before surgery to reduce the size of the tumour and make it easier to remove with surgery, this is called neoadjuvant radiotherapy. In some cases, radiotherapy and chemotherapy are given in combination. Sometimes radiotherapy is justdone to control the cancer, as cure is not realistic, with this treatment it is often possible to limit the growth or spread of the cancer so that it progresses less rapidly. And the patient is asymptomatic for some time. This is called palliative radiotherapy.

There are two main types of radiotherapy:

  1. External radiotherapy is the most common type, where the radiation comes from a machine from outside the body. The machines used emit radiation - usually high-intensity X-rays, but other types of radiation are also used.
  2. The treatment course is planned by a specialist (radiation oncologist), which is based on the type, size and location of your cancer. The total dose of radiation needed to treat the cancer is carefully calculated. The total dose is often divided into many fractions. Usually the plan is then to have a short session of radiotherapy treatment on most days each week, for several weeks. You receive a fraction of the total dose of radiation at each separate treatment session.

    Treatment sessions continue until you have had the total dose or radiation. By having a small fraction of the total dose on many sessions, it is more likely to work better than having the whole dose at one session, and reduces the severity of side-effects.

    During each treatment session, the aim is to get as much of the radiation as possible to focus on cancerous cells, with as little radiation as possible to affect normal cells. The technology of radiotherapy has improved in recent years. Modern scans such as MRI and CT scans can define the position of tumours much more accurately than in the past. The beams of radiotherapy can, therefore, often be accurately focused on the tumour, with less damage to nearby normal tissue than in the past. So, in recent years, this has increased the effect of radiotherapy treatment whilst reducing side-effects.

    Before the first session, your specialist will carefully plan the exact direction and approach of the radiation from the machine, and the exact position you need to lie in for each session of treatment. The specialist may mark a site on your skin with permanent ink. This is the target and ensures that during each treatment session the radiation is aimed at the same spot. Sometimes a more permanent tiny tattoo is used for the same purpose.

    Sometimes a special cast is made which is put over the area to be treated during each treatment session. A mark is placed on the cast (instead of on the skin) as the target for the radiation machine to aim at. A cast is particularly useful for treatment of certain cancers of the head and neck. The cast keeps the head perfectly still and in the same position for each treatment session.

    You may be asked to put on a hospital gown for each treatment session. The treatment is given in a special radiotherapy room. You will usually lie on a couch and the radiation machine is positioned above you. The therapist may adjust your position and adjust the angle and position of the machine so that when it emits radiation the rays are focused at exactly the right part in your body (through the mark on your skin or cast). Lead shields may be placed over certain areas of your body to protect them from the radiation.

    When you are settled, the therapist has to go out into a separate control room. This is for their protection from repeated exposure to radiation. In the control room they can see you via a TV monitor or through a window, and you will still be able to talk to them. The therapist then uses controls to emit radiation from the machine for a short time.

    Each session of treatment usually only lasts a few minutes (although it may take several minutes to position you and the machine correctly each time). During each treatment session the radiation may be emitted several times in short bursts from different angles. This may mean that you need, or the machine needs, to be adjusted a few times during a treatment session. One reason why this may be done is that, although each burst of radiation will focus on the cancer, each burst will pass through different parts of your body on the way. This aims to reduce damage to normal tissues.

    The actual X-rays do not hurt. You do not feel the radiation going through your body and it is not hot. (Just like an X-ray test such as a chest X-ray is painless.) However, a skin reaction may develop at the site of radiotherapy days or weeks after starting a course of external radiotherapy. That is, the skin through which the X-rays have passed can become red, sore or itchy. Some people describe recent surgical scars and wounds on affected skin also becoming painful at some point during a course of radiotherapy. If this occurs, then mention it to your doctor or specialist.

  3. Internal radiotherapy, which nvolves inserting a small radioactive implant into the cancerous tumour or next to the tumour. The implants come in different shapes and sizes (small rods, pellets, etc), and can contain different radioactive materials. An anaesthetic may be needed to allow the doctor to place the implant in the correct place. Radioactive implants are used mainly for some cancers of the uterus, vagina, rectum, cervix, prostate, mouth and neck. This is sometimes called brachytherapy.
  4. Some types of implant are removed after a few days. Some types are only left in place for a few minutes. Some types are left in place long-term. For example, radioactive 'seeds' are sometimes placed into prostate tumours and are left indefinitely.

    In some situations radioactive liquid, for example, treatment for thyroid cancer involves taking of a drink which contains radioactive iodine. The radioactive iodine is absorbed into the bloodstream and taken up by thyroid cells (both normal and cancerous). The radioactive iodine then concentrates and builds up in thyroid cells. This then destroys the thyroid cells, but has little effect on any other tissue in the body.

Unlike a popular perception, externalradiotherapy does not make you radioactive. However, for internal radiotherapy, whilst a radioactive implant is in place you will be emitting a certain amount of radioactivity. This is the reason that your movements may be restricted andvisitors not allowed whilst certain types of implant are in place. However, most of the radioactivity is concentrated around the tumour being treated. Once the implant is removed, you no longer emit radioactivity.

Radiotherapy aims to kill or damage cancer cells, but some normal cells may get damaged which can lead to side-effects.

  • The most common side-effect that people experience after radiotherapy is tiredness. This can even start after your radiotherapy is completed.
  • Some people develop a local skin reaction days or weeks after having external radiotherapy.
  • Possible side-effects depend on the area of the body being treated. For example: radiotherapy to a tumour in the the neck may cause a sore mouth; radiotherapy to the abdomen may cause diarrhoea; etc.

Your specialist will normally discuss with you the possible side-effects that may occur following radiotherapy to the particular area of your body being treated.

It is well known that radiation is a risk factor to developing certain cancers. Some people are concerned that radiotherapy treatment for a cancer may itself cause a second cancer. However, a recent research study has provided some reassuring results. The study looked at over 640,000 cancer patients who had been treated with radiotherapy. The study concluded that, on average, about 5 in 1,000 people who had undergone radiotherapy treatment developed a subsequent cancer within 15 years as a result of the radiotherapy. The risk varied somewhat, depending on which part of the body was treated. (Some parts of the body seemed to be more prone than others to a second cancer caused by radiotherapy.) However, the overall low risk is reassuring, especially when you compare it with the benefit of radiotherapy.


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