See glossary pages 33 to 36 “ASN has ensured the oversight of medical applications of ionising radiation since 2002. After having put in place entirely new regulations in the area of patient radiation protection, ASN realigned its inspection programme on radiotherapy treatment safety as of 2007.” Jean-Christophe Niel Former Director-General of ASN Director-General of IRSN In 2005, France discovered its most serious ever medical accident involving ionising radiation, when cancer patients undergoing radiotherapy treatment received excessive doses of radiation, with severe clinical consequences. The investigation revealed several dysfunctions in the delivery of the radiotherapy treatment, as well as a lack of understanding of the treatment protocols. Épinal hospital, the risks elsewhere than in nuclear facilities What is dosimetry? Dosimetry in radiotherapy is the calculation of the radiation doses to apply to the area to treat and the treatment duration. Scientific studies have determined the radiotherapy doses to administer according to the type and stage of the cancer, the organ to treat, the age of the patient and their prior treatments. These are standard doses. The radiation oncologist also specifies the acceptable dose limits for the organs at risk situated near the tumour. As well as determining the types of rays to use and the size and direction of the beams, the dosimetry phase also involves determining, by a computerised study, the distribution of the radiation dose to apply to the area to treat to optimise the irradiation and treatment of the tumour while sparing the neighbouring healthy tissues. Source: INCa In early 2005, an unexpected frequency of complications linked to radiotherapy treatments carried out at the Jean Monnet Hospital in Épinal was discovered, concerning in particular 24 patients treated for prostate cancers between May 2004 and August 2005. This serious accident, rated 7 on the ASN-SFRO scale, was attributed to incorrect utilisation of the treatment planning software: in May 2004, the radiotherapy protocol for the treatment of prostate cancers was modified to get the best out of the possibilities of the dosimetry software. This change also implied modifying the parameters used in the calculation of irradiation intensity, which was not done for some of the patients. Having discovered, as of January 2005, more frequent complications than expected, the use of this protocol was finally stopped in August 2005. Serious human consequences Of the 99 patients treated using this protocol between May 2004 and August 2005, 24 received a dose that was 20 to 30% higher than the prescribed dose. Twelve of these patients suffered from severe radiation-induced complications, such as intense pain and radiation necrosis lesions causing fistulas, discharges or haemorrhaging necessitating repeated blood transfusions. Ten of these patents died as a result of these complications. The other patients were affected less severely. The patients and their families expressed the feeling of having been abandoned, having received no social, economic or psychological support. The inquiry revealed other dysfunctions leading to significant overdoses. Between 1989 and 2000, a problem with the parameter settings of another treatment planning software, designed and produced in-house, led to slightly longer irradiation times. Of the 5,000 cancer patients treated at the Épinal hospital centre during this period, about 300 received a dose excess of more than 7%. Two of these patients died as a result of the complications resulting from the treatment. This parameter setting error was corrected in 2000. Between October 2000 and October 2006, the failure to take into account in the dosimetric calculation the irradiation delivered when taking images to check positioning led to overdoses of 8 to 10% with respect to the prescribed dose for 409 patients. Two of these patients died as a result of the complications resulting from the treatment. 22 • Les cahiers Histoire de l’ASN • November 2023
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