Definition

Brachytherapy, also called brachytherapy (from the Greek brachy, “short”), is a form of radiotherapy consisting of placing radioactive elements (iridium or cesium) directly inside the body, either in contact with the tumor or in the body. tumor itself. This allows the tumor to be irradiated directly and in high doses. Thanks to this very targeted action, the side effects are less.

Depending on the position of the radioactive sources, there are two forms of brachytherapy:

• plesio-therapy (endocavitary or endoluminal brachytherapy): the radioactive sources are placed in a natural cavity, in contact with the tissue to be irradiated. This is particularly the case with utero-vaginal brachytherapy used to treat cancer of the cervix or vagina. Radioactive sources are placed in an applicator inserted deep in the vagina;
• interstitial brachytherapy or endocuritherapy: the radioactive sources are implanted in the tissue, at the very heart of the tumor, by means of fine catheters. This technique can be used for a tumor of the tongue, the prostate, the anus in particular.

The main principles

Brachytherapy is based on the principles of radiotherapy, a treatment that uses radiation, or “rays”, to destroy cancer cells by blocking their ability to multiply.

Brachytherapy represents 5% of radiation treatments.

Brachytherapy is possible in certain localized cancers with specific indications:

• gynecological cancers: vaginal cancer, cervical cancer, endometrial cancer;
• prostate cancer;
• cancers of the penis;
• cancers of the tongue, tonsils;
• breast cancer;
• skin cancer;
• bronchial cancer;
• esophageal cancer;
• anal cancer.

Gynecological and prostate cancers represent 76% of the indications for brachytherapy.

Depending on the indication, brachytherapy can be used to destroy the last cancer cells after surgical removal of the tumor, or on the tumor itself. It is sometimes associated with conventional radiotherapy treatment.

The sessions take place in the radiotherapy department. They are conducted by a brachytherapist, radiotherapist oncologist specializing in brachytherapy.

Brachytherapy requires the installation of a non-radioactive vector device. Or, for the main cancers treated with brachytherapy:

• for cervical cancer, the applicator is positioned in the vagina, usually under general anesthesia;
• for prostate cancer, the radioactive sources are placed inside the prostate under general anesthesia or spinal anesthesia. An endorectal ultrasound makes it possible to guide the implantation of needles intended to introduce the radioactive sources, via the perineum. They can be either definitive implants (iodine 125 grains) or temporary implants connected to a source projector most often containing a micro-source of iridium 192. Regarding permanent implants, their radioactivity decreases. over time and does not constitute a danger, neither for the patient, nor for those around him.
• for endometrial cancer, the applicator containing the radioactive source is introduced either into the vagina (to destroy cancer cells that may remain after removal from the uterus or in the uterus (if the brachytherapy targets the tumor) herself). 

Then in an automated and computerized manner, the source projector will inject the radioactive source into the applicator. Depending on the dosimetry (dose delivered and irradiation time), different types of treatment are distinguished:

• high dose rate brachytherapy (HDR): high doses are delivered over a few minutes several times, at the rate of one to several sessions per week. Hospitalization is generally not necessary;
• low dose rate brachytherapy (LDR): radioactive sources are left in place for several days, during which hospitalization is necessary;
• pulsed low flow brachytherapy: the probe moves step by step through the tissues to be irradiated and delivers a pulse (5 to 45 minutes) every hour, 24 hours a day.

The beginnings of brachytherapy date back to 1901, a few years after the discovery of radioactivity. In 1905, the beneficial action of radium rays for skin and cervical cancer was recognized. In the 20s, in collaboration with the Curie laboratory, radioactive needles were applied to diseased tissues or to molded supports suitable for the areas to be treated.