¿Qué es la Radioterapia?
Radiation oncology involves using high-energy ionising radiation that alters cancer cells’ ability to divide. It can be administered as a curative or palliative therapy, or as an adjuvant to other techniques.
In high doses, radiotherapy destroys cancer cells or slows their growth as it damages their DNA. Cancer cells with damaged DNA stop dividing, or die. When the damaged cells die, they are broken down and rejected by the body.
Radiotherapy may be necessary in the following scenarios:
- As a curative treatment for cancer. It can be used alone or in combination with a radiosensitiser to make it more effective, for example with chemotherapy, immunotherapy or other systemic treatments. The aim is to cure and control the tumour while preserving nearby healthy tissues/organs.
- As an additional treatment following surgery (known as adjuvant radiotherapy). It can also be administered alone or in association with systemic treatments. The aim is to reduce the risk of recurrence of any cancer cells that may persist after the initial treatment.
- As a treatment before surgery (neoadjuvant radiotherapy, administered alone or in combination). The aim is to achieve more effective surgical treatment.
- As a palliative treatment, to alleviate symptoms or improve patients’ quality of life, reduce tumour size, manage pain, prevent bleeding, etc.
Radiotherapy has advanced in recent years, improving in terms of efficacy and precision. This is due to technological advances with new-generation equipment that incorporates increasingly more sophisticated elements. These allow the irradiation to adapt to the shape of the tumour, synchronise with the movements of the organs and reduce the safety margins to a minimum, thus reducing secondary effects on healthy tissues.
Radiotherapy may be administered in the following ways:
- External radiotherapy. A device known as a linear particle accelerator is used to emit and direct high-energy beams towards the tumour from outside the body. This is the standard technique applied to all tumour sites.
Different techniques are used to perform these types of treatments:
- Three-dimensional conformal radiotherapy (3D-CRT).
- Image-guided radiotherapy (IGRT). The aim is to verify the daily positioning, monitor changes in tumour volume and how it interacts with healthy tissues. In prostate tumours, fiducial markers (radiopaque markers that are placed inside the prostate for correct assessment and localisation) are used.
- IMRT (intensity modulated radiotherapy). This technique allows for better dose conformation in tumours and lower doses in healthy tissues by modulating the beam.
- VMAT (volumetric modulated arc therapy). This is a development of the intensity modulated radiotherapy (IMRT) technique that allows greater safety to be achieved in the shortest possible time.
- SABR/SBRT (stereotactic ablative radiotherapy). This technique allows a high dose of radiotherapy to be administered per session, in a small number of fractions (3-8), achieving a high local response rate that is comparable to surgery.
- FSRT (Fractionated stereotactic radiation therapy) is intercranial SBRT. It is a technique that allows a high dose of radiotherapy to be administered per session, in a small number of sessions. A very precise but non-invasive cranial immobilisation system is used. A posterior thermoplastic mask and an open-vision anterior mask are used to fix the position of the patient’s head.
- Deep inspiration breath hold (DIBH). This radiotherapy technique involves patients breathing deeply during treatment and holding their breath as radiation is delivered. When you inhale deeply, your lungs fill with air and your heart moves away from your chest. DIBH may be useful in situations where radiotherapy needs to be applied to the chest region, and doses of radiation to the heart should be avoided.
- Total body irradiation (TBI) in treatment to prepare the patient for bone marrow transplantation.
- Superficial therapy. This is a type of low-energy radiotherapy that only penetrates a short distance beneath the surface of the skin. It is highly effective, painless and leaves no marks or scars. It can be applied to skin tumours with excellent aesthetic results.
- Brachytherapy. This type of radiotherapy consists of placing a radioactive source inside the tumour or nearby cavities using special applicators. The advantage is that it allows high curative doses to be administered to the area in need of treatment, while significantly reducing the dose that reaches neighbouring healthy organs. The main indications are cervical, endometrial, breast and prostate cancer, either on its own or in association with external radiotherapy.
- Intraoperative radiation therapy (IORT) It is performed using a mobile electron linear accelerator that is installed in the operating theatre. This technique allows irradiation to be applied precisely with minimal exposure to healthy tissue, which is displaced and protected during the process. The potential advantage is offering treatment exclusively at the time of surgery, with no need for external irradiation, and therefore eliminating the need to travel to the hospital afterwards.
There are a number of general tips that may help with radiotherapy treatment:
• Wash the skin every day with pH-neutral soap and/or oils.
• Drink at least 1.5 litres per day.
• Apply moisturising cream (alcohol- and perfume-free are recommended).
• Use a neutral, paraben-free deodorant.
• Avoid hot showers.
• Avoid direct sunlight, and use sun cream with a high protection factor.
• Shave preferably with an electric razor instead of a razor blade.
Depending on where the irradiation site is, specific recommendations for nutrition, hydration, controlling bowl movements, diet, and dental/oral care and hygiene will be given.
Radiotherapy treatment is always individualised, in other words, each patient has their own specific treatment.
Before starting the treatment itself, it must be planned with the aim of determining a series of parameters that will vary depending on the type of tumour, the location and extent, as well as the individual characteristics of each patient.
First of all, the most suitable position for the treatment must be determined. Once defined, the patient is immobilised using different materials (thermoplastic mask, chest immobiliser, etc.) to allow this position to be reproduced every day of the treatment.
Next, with the patient immobilised, a planning CT (computed tomography) scan is performed, which sometimes requires contrast to be injected. The radiation oncologist uses this procedure to determine and locate the volume to be treated and the healthy structures that are to be protected from radiation.
In this process, reference marks are made on the skin (tattoos) to allow the same conditions to be reproduced during the treatment. These tattoos are done in ink (a shallow, painless puncture), and are dot-shaped and permanent. They help radiotherapy staff to position the area to be treated with more accuracy.
Once all the necessary examinations are complete, the treatment is prepared. Radiophysicists and dosimetry technicians carry out the calculations necessary to determine the correct dose to administer. These calculations are different for each patient and depend on many factors.
Once the treatment has been prepared and verified, the technicians administer it guided by the immobilisers used in the CT and the tattoo points.
Once in place, a verification image is taken and any necessary corrections are made in order reproduce the patient's planned treatment on a daily basis.
The therapy is administered in outpatient sessions at a treatment centre or hospital in special rooms known as ‘radiotherapy rooms’ or ‘bunkers’. This is where the radiotherapy machines (linear accelerators) are located, and they have special walls that provide perfect insulation to prevent radiation from escaping.
During radiotherapy treatment, the patient will be accompanied by the following team of professionals who will help and care for them:
• Radiation oncologist. A medical specialist who treats different tumours with radiation.
• Radiophysicist. A physics specialist who is responsible for making sure the equipment used to deliver the radiation works properly, and ensures that the correct dose of radiation is administered.
• Dosimetrist technician. This is the member of healthcare staff who collaborates with the radiophysicist to plan treatment and monitor machines.
• Radiotherapy nurse. They accompany the patient during treatment and provide any necessary information. They also take care of the patient and, along with the radiation oncologist, treat any side effects that may arise.
In each session, the patient must be placed in the same position as during the simulation, using the immobilisers and tattoo points, then image verification of the treatment position is carried out (with appropriate modifications where needed). Once verified, the treatment is performed. Each session lasts just a few minutes, although this may vary depending on the technique.
It is very important that the patient does not move during the whole session, so that the radiation is always directed at the same part of the body.
The specialist medical staff do not enter the treatment room while the machine is in operation. Instead they monitor the patient via a television screen and, if necessary, can communicate with them via an intercom.
Treatments vary in duration, from a single session to more than 30 sessions. For longer treatments (several weeks), sessions take place on a daily basis, from Monday to Friday. In shorter treatments, the pattern of administration can vary. It depends on the type of treatment and its location.
A person who receives external radiation is not left with radioactive material and does not need to follow any special safety precautions at home.
The patient must remain still so that the radiation goes to exactly the same place every time. Radiation will be administered for one to five minutes. Patients can breathe normally during this time.
Coloured lights may be seen directed towards the marks on the skin. These lights are harmless, and are used to aid positioning during treatment.
The radiation machine can be stopped at any time. Radiation cannot be heard, seen or smelled.
Information and psychological support help with understanding the process and improving quality of life. Patients are advised to raise all doubts with the team of professionals involved in their radiotherapy before turning to the internet or other sources of information that are not adapted to each specific case.
It is a treatment that may have short-term side effects, but chronic side effects that appear in the long term are also possible. Side effects do not always occur, and when they do the severity differs from person to person. They depend on the dose administered, and especially on the region of the body treated. When they do appear, they tend to do so after several sessions, not at the start of treatment. The radiation oncologist and radiation nurse inform the patient of the potential side effects at the first consultation
Short-term effects (acute toxicity) usually resolve within a few weeks or months after the end of treatment, and include the following:
• Skin reactions similar to sunburn in the areas treated. After two to three weeks, a reddish discolouration (erythema) appears, which will disappear a few weeks after the end of the treatment.
• Hair loss. Hair loss is temporary and only occurs in the irradiated area. It begins within 2-3 weeks, and grows back after 3-6 months.
• Mouth ulcers that may cause pain when swallowing, and improve by rinsing with thyme water. These same ulcers can appear in the oesophagus, causing pain when swallowing, or in the intestine, causing nausea, vomiting, diarrhoea, inflammation of the rectum or a feeling of needing to defecate.
• Injury to the genitourinary system (bladder, urethra, vagina) or respiratory system, causing a cough, expectoration or difficulty breathing.
Long-term side effects (long-term toxicity) are uncommon but not completely eliminated, and include the following:
• Heart involvement such as pericarditis or ischaemic heart disease (depending on the dose administered to the heart and the patient’s own vascular risk factors, with smoking being one of the most important).
• Nervous system involvement, with manifestations such as drowsiness and memory loss.
• Genitourinary system involvement, for example urinary retention or incontinence, blood in the urine, vaginal dryness, decreased libido or erectile dysfunction.
• Digestive system involvement, including inflammation of the rectum or anus, discomfort when defecating or blood in the stool.
• Respiratory involvement: pulmonary fibrosis, which is usually asymptomatic or only causes a dry cough and has a specific treatment.
- Pregnancy and radiotherapy
Pregnant women can receive radiotherapy, but some important aspects must be considered. High doses of radiation can harm the baby at any time during pregnancy. This can cause miscarriages, birth defects, delayed foetal development or an increased risk of childhood cancer. For this reason, doctors do not use radiotherapy during pregnancy.
The administration of radiotherapy during pregnancy may pose a potential risk to the foetus, even if it does not directly receive the radiation beam, as the treatment produces scattered radiation.
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