Radiotherapy

What is it ?

Radiotherapy is a cancer treatment that uses the properties of ionizing radiation against tumor cells. This radiation induces damage to the DNA. The rays can’t completely spare healthy cells, but these cells have the ability to repair their DNA afterward, unlike tumor cells, which are more vulnerable. Les rayons ne peuvent pas totalement épargner les cellules saines.

Rays cannot completely spare healthy cells.

The effect of radiotherapy is local (only where the rays are directed). Surgery also has this effect.

Finally, its effect can be synergistic with other treatments, particularly chemotherapy.

How it works ?

Radiotherapy treatment requires complex and technical preparation by the radiation oncologist and medical physicists.

Depending on the indication and the organ, the doctor prescribes the treatment (dose of radiation in Gray and number of sessions).

Before any treatment, a radiologist performs a centering CT scan on the patient. This allows for precise determination of the tumor's location and volume to be treated.

Next, simulations are performed on a computer to calculate how to deliver the correct dose to the right area while sparing as much as possible the healthy organs surrounding the cancer. Each patient therefore receives a tailored treatment.

Once the treatment plan is established, the setup occurs during the first session.

This session may be longer than the others, as it involves determining the exact position to be maintained during each session.

The medical team may use positioning devices (marker pen markings, tattoo points) as well as immobilization devices (face mask). These methods ensure that the position remains consistent from one session to the next.

Most often, this treatment is administered on weekdays (5 sessions per week). The rays are invisible, odorless, and painless. Each session lasts about 10 minutes.

There are specific subtypes of radiotherapy, such as :

• Brachytherapy, which involves temporarily implanting a radioactive source in direct contact with the tumor
• Stereotactic radiotherapy, which is a high-dose and highly focused form of radiotherapy. It is reserved for small lesions (fewer sessions needed but lasting about 45 minutes each).

Bernard, 61, shares his experience with his battle against prostate cancer and his treatment with radiotherapy.

Side effects

Side effects of radiotherapy can be observed only in the treated area. The radiation from the therapy also damages the tissues it passes through.

Most of these effects are acute. They appear about a week after the start of treatment and resolve within a few days to a few weeks after the end of the irradiation.

The most common effect is radiation dermatitis, which resembles a sunburn.

However, it still depends on the organ being treated with radiotherapy.

Less commonly, chronic side effects may persist or emerge over time. Again, their nature depends on the irradiated area.

To prevent and manage these side effects as effectively as possible :

• Radiotherapy technicians will ask you questions daily at the treatment station.
• A radiation oncologist will see you for a consultation once a week (or more frequently if needed). This consultation will help identify any side effects and offer symptomatic treatment if necessary.

In all cases, it is important to avoid interrupting the treatment as much as possible.

Indications

Radiotherapy can be used at different stages of the disease :

• As a curative treatment, where radiotherapy alone can destroy the tumor, such as in certain lung tumors. It may also be combined with concurrent chemotherapy, for example, in cervical cancer.
• As an adjuvant treatment, meaning it complements the radical local treatment (surgery) to reduce the risk of local-regional recurrence, for example, after a lumpectomy.
• As a palliative (symptomatic) treatment for advanced diseases, particularly to address painful tumor lesions (bone metastases or lymph nodes).