ASN Report 2020

3. Brachytherapy Brachytherapy can be used to treat cancerous tumours either specifically or as a complement to another treatment technique. Brachytherapy consists in implanting radionuclides, exclusively in the form of sealed sources, either in contact with or inside the solid tumours to be treated. The main radionuclides used in brachytherapy are iridium-192 and iodine-125. Brachytherapy uses three techniques (detailed below), depending on the indications. 60 brachytherapy centres are licensed by ASN, and 50 of them use the High Dose-Rate (HDR) technique. ASN issued 13 licenses in 2020. The majority of them were updates to an existing license. 3.1  Description of the techniques 3.1.1 Low Dose-Rate (LDR) brachytherapy ∙ delivers dose rates of between 0.4 and 2 grays/hour (Gy/h); ∙ by means of permanently implanted iodine-125 seeds or temporarily implanted caesium-137 seeds. Indications: ∙ Treatment of prostate cancers. Permanent implantation in the patient’s prostate gland of seeds with a unit activity of between 10 and 30 megabecquerels (MBq). A treatment requires about 100 seeds, representing a total activity of 1 to 2 gigabecquerels (GBq). ∙ Treatment of certain eye tumours by temporary implants of iodine-125 placed in a silicone insert (8 to 24 grains per disk), enclosed in a gold-titanium plaque. The seed size is the same as for prostate treatment, but the activity is higher (about 200 MBq per grain). The implants are put in place in the operating theatre under general anaesthetic and the treatment lasts from 1.5 days to one week, with hospitalisation of the patient. ∙ Treatment of tumours of the endometrium or the uterine cervix by brachytherapy with caesium-137. The treatment is delivered in a shielded hospital room using a caesium-137 afterloader (activity of about 8.2 GBq). The treatment involves 2 to 5 days of hospitalisation. This technique is used very little, pulsed dose-rate brachytherapy being the preferred treatment. 3.1.2 Pulsed Dose-Rate (PDR) brachytherapy ∙ delivers dose rates of between 2 and 12 Gy/h; ∙ using sources of iridium-192 with a maximum activity of 18.5 GBq and applied using a specific afterloader. Indications: mainly gynaecological cancers, more occasionally bronchus or oesophageal cancer, and exceptionally breast and prostate cancers. This technique requires patient hospitalisation for several days in a room with radiological protection appropriate to the maxi- mum activity of the radioactive source used. It is based on the use of a single radioactive source which moves in steps, and stops in predetermined positions for predetermined times. The doses are delivered in sequences of 5 to 20 minutes, sometimes even 50 minutes, every hour for the duration of the planned treatment, hence the name PDR brachytherapy. Pulsed dose-rate brachytherapy offers a number of advantages with regard to radiation protection: ∙ no handling of sources; ∙ no continuous irradiation, which enables the patient to receive medical care without irradiating the staff or having to interrupt the treatment. However, it is necessary to make provision for accident situations related to the operation of the source afterloader and to the high dose-rate delivered by the sources used. 3.1.3 High Dose‑Rate (HDR) brachytherapy ∙ delivers dose-rates in excess of 12 Gy/h; ∙ using sources of iridium-192 with a maximum activity of 370 GBq and implemented with a specific afterloader (some afterloaders use a high-activity cobalt-60 source) Indications: mainly gynaecological cancers, occasionally the treatment of prostate and bronchus cancers, and exceptionally ear, nose and throat cancers. This technique is also indicated in the treatment of keloid scars. This technique does not require the patient to be hospitalised in a room with radiological protection; it is performed on an out- patient basis in a room with a configuration comparable to that of an external-beam radiotherapy room. The treatment is performed with an afterloader containing the source and involves one or more sessions lasting a few minutes, spread over several days. 3.2  Technical rules applicable to brachytherapy installations The rules for radioactive source management in brachytherapy are comparable to those defined for all sealed sources, regardless of their use (see point 3.3.3). Low Dose-Rate brachytherapy In cases where permanent implant techniques are used (seeds of iodine-125 in particular for treating prostate cancer), the applications are carried out in the operating theatre with ultrasonography monitoring, and do not require hospitalisation in a room with radiation protection. Pulsed Dose-Rate brachytherapy This technique uses source afterloaders (generally 18.5 GBq of iridium-192). The treatment takes place in hospital rooms with radiological protection appropriate for the maximum activity of the radioactive source used. High Dose-Rate brachytherapy As the maximum activity used is high (370 GBq of iridium-192 or 91 GBq of cobalt-60), irradiation can only be carried out in a room with a configuration comparable to that of an external- beam radiotherapy room. 3.3  Radiation protection situation in brachytherapy In the same way as for external-beam radiotherapy, the safety of brachytherapy treatments has been a priority area of ASN oversight since 2007. The management of high-activity radioactive sources is moreover a specific concern in this activity. The inspection programme was severely impacted in 2020 by the Covid‑19 health crisis. Sixteen inspections were performed out of the 25 initially scheduled, representing about a quarter of the departments. By way of comparison, two-thirds of the departments had been inspected over the last two years. Among the inspections carried out in 2020, seven were conducted remotely, including three with on-site inspection part. 220 ASN Report on the state of nuclear safety and radiation protection in France in 2020 07 – MEDICAL USES OF IONISING RADIATION