ASN Report 2018

3 —  Brachytherapy Brachytherapy allows specific or complementary treatment of cancerous tumours, particularly in the head and neck, the skin, the breast, the genitals and the bronchial tubes. This technique 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 techniques involve three types of applications. Sixty-two brachytherapy centres are licensed by ASN, and 47 of them use the High Dose-Rate (HDR) technique (see point 3.3.1.). ASN issued 26 licenses in 2018. The majority of them concerned the updating of 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 iodine-125 sources in the form of permanently implanted seeds. These iodine-125 sources (seeds) are used to treat prostate cancers. The seeds - which are implanted permanently in the patient’s prostate gland - have unit activity levels of between 10 and 30 megabecquerels (MBq), and as a treatment requires about one hundred seeds, this gives a total activity of 1 to 2 gigabecquerels (GBq). 3.1.2  –  Pulsed Dose-Rate (PDR) brachytherapy ∙ ∙ delivers dose rates of between 2 and 12 Gy/h; ∙ ∙ using sources of iridium-192 displaying a maximum activity of 18.5 GBq and applied using a specific afterloader. This technique requires patient hospitalisation for several days in a room with radiological protection appropriate for the maximum 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 pulsed dose-rate brachytherapy. Medical prescription errors in radiotherapy So-called «wrong side» (or laterality) errors are frequent causes of ESRs reported to ASN and most often rated level 2 on the ASN‑SFRO scale. ASN, in collaboration with the professionals, published a radiotherapy patient safety bulletin on this subject (Bulletin No. 6) in 2014. Since then, out of a total of 26 events rated level 2 and two events rated level 2+ over the 2014‑2018 period, 7 «wrong side» errors have been reported, 3 of them in 2018. Further work on this subject will be conducted with the SFRO and the SFPM (French Society of Medical Physics) in 2019. Example of an event concerning a laterality error in a breast cancer treatment (left breast): The consultation report first indicates the left breast, then ends by mentioning the right breast. The prescription document was then drawn up with a laterality reversal: «right breast» indicated instead of «left breast»: the conventional treatment process was carried out, ordered on an incorrect prescription. Factors contributing to this event: ཛྷ ཛྷ the absence of surgical clips (*) ; ཛྷ ཛྷ the poorly visible scar on the left-hand side; ཛྷ ཛྷ the lack of an injection of patent blue dye (**) to look for sentinel ganglions which would have alerted the radiographers. Observed clinical consequences: ཛྷ ཛྷ overall treatment (surgery, chemotherapy, radiotherapy, hormone therapy) sub-optimal for the left breast; ཛྷ ཛྷ irradiation of healthy tissue of the right breast. It should be noted that the entire treatment was delivered to the patient without checking the prescription against the other mandatory medical file documents (operative report, pathological anatomy report and minutes of the multidisciplinary consultation meeting). * Surgical clips are metal clips that make it easy to relocate the areas to be treated by radiotherapy after conservative surgery (case of breast cancer). ** Patent blue dye is a diagnostic medication used to identify sentinel ganglions prior to a biopsy (breast cancer). SUMMARY In external-beam radiotherapy, the improvement in treatment safety, which has been seen for several years now, is continuing. It is nevertheless still confronted with major technological changes, bringing potential risks if the organisational and human factors are not correctly controlled. These technological changes necessitate prospective risks studies, but the methodology is not yet fully mastered by the professionals. ASN moreover observes that, after a significant increase in ESR notifications in this area of activity, the number has been falling steadily over the last three years. The causes of this reduction must be identified. 212  ASN report on the state of nuclear safety and radiation protection in France in 2018 07 – MEDICAL USES OF IONISING RADIATION