Radiotherapy is a treatment often used in cancerology. It uses ionizing radiation in exactly the same way as diagnostic radiology (chest X-ray, CT scan, etc.), but at a higher dose. This dose is measured in Grays (Gy).
The principles of radiotherapy
The two fundamental principles of radiotherapy are :
- deliver a sufficient dose to the organ concerned, either after removal of the tumour (surgery) or on the tumour in place, so as to destroy it,
- to spare surrounding healthy tissues as much as possible (skin, muscles, but also noble organs such as the liver, digestive tract, etc.).
What is radiotherapy used for?
It can be performed for curative purposes, with a view to healing.
- or in combination with other treatments, usually after surgery. It is then used to reduce the risk of recurrence.
- or exclusively (more or less in conjunction with concomitant chemotherapy). In this case, the tumor is destroyed directly and completely, without surgery.
It can be performed for palliative or symptomatic purposes.
It enables local treatment of one or more cancerous lesions that could not be operated on, with the aim of improving a symptom caused by these lesions.
A distinction is made between radiotherapy :
- To reduce pain (analgesic radiotherapy), generally in a few sessions over two weeks, performed on a painful lesion.
- To recover or avoid paralysis (decompressive radiotherapy), also in a few sessions over two weeks, performed on a lesion compressing the spinal cord or a nerve root.
- "Closing" when some tumor lesions grow despite chemotherapy treatment. In these cases, radiotherapy is usually highly targeted (stereotactic radiotherapy).
In all cases, the dose delivered and the exact number of sessions is calculated on a case-by-case basis.
How does radiotherapy work? What are the different techniques?
Radiotherapy is said to be EXTERNAL, when the source of ionizing radiation is located at a distance from the patient. This requires a CT scan to be carried out in the radiotherapy department, to target the rays on the area to be treated.
Several different techniques are available:
- Conventional conformal radiotherapy,
- Stereotactic radiotherapy (Cyberknife ®),
- Proton therapy.
A more detailed data sheet exists for each of the radiotherapy techniques mentioned.
Radiotherapy is said to be INTERNAL, when the source of ionizing radiation is located directly in the area to be treated.
A distinction is made between :
- Intrabeam ®,
- Brachytherapy.
A more detailed data sheet exists for each radiotherapy technique.
Technical constraints, safety measures
The study of the biological effects of ionizing radiation shows that any underdosage above 5% increases the risk of cancer recurrence, while an overdosage above 5% is likely to lead to severe clinical complications. Physicists, radiotherapists and radiotherapy technicians work together to ensure the safety and efficacy of treatment.
Radiotherapy is a personalized treatment, tailored to each individual's anatomy and tumor type. It may sometimes be necessary to immobilize a part of the body in a custom-made mold. In all cases, the scan is performed in the position that will be used for each session. In this way, the machine's settings (based on the scan) correspond to the patient's actual position during the session.
Each treatment is validated by a doctor and a physicist before the sessions begin.
The patient's correct installation on the treatment device is checked several times a week by means of X-rays (or scans) taken just before the session. Similarly, the dose delivered during a session is also monitored by a sensor placed on the patient.
What are the side effects?
Side effects depend on the area treated, the technique used and the dose. They occur only in the area of the body receiving the rays (surface and depth), and never at a distance. They will be explained to you during your initial consultation.
There are two types of side effects:
- Those that occur during radiotherapy and disappear spontaneously in the weeks following the treatment.
- Those that occur after radiotherapy, and which will not disappear spontaneously. They may appear years after the end of radiotherapy.
Here are some common side effects, by way of example:
| SKIN | Redness, burning sensations, sometimes painful. Sun protection is essential (total sun block during and for a year after the end of radiotherapy). |
| HAIR and COAT | Partial or total hair loss: on the head, hair loss is often difficult to bear psychologically, and can be compensated for by wearing a scarf or a hair prosthesis. |
| LOWER VENTER and BASIN | Diarrhea, stomach ache, frequent urination, etc. |
| TRONC | Cough, sputum, mimicking viral bronchitis. |
Do not use any creams or medicines without the agreement of the radiotherapy department, as there is a risk of increased side effects.
Talk to the team and we will suggest solutions.