ESTRO 36 Abstract Book

S99 ESTRO 36 _______________________________________________________________________________________________

radiotherapy is harnessed to convert the tumor into an individualized cancer vaccine. Overall, while radiation has emerged as a promising partner for immunotherapy and current research is focusing at identifying tumor and patient characteristics that can predict which patients should receive upfront the combination of immunotherapy with radiotherapy instead of immunotherapy alone.

their practices, and the current percentage of acceptable results exceeds 97%. With the development of advanced radiotherapy technologies resulting in greater complexity of radiation treatments, it was necessary to extend basic dosimetry audits. More complex audit programmes involve tests of different beam parameters, machine performance characteristics and treatment delivery techniques. Examples include audits of small beam dosimetry, complex irradiations, combined beams, audits of treatment planning, and ‘end-to-end’ methodologies. Although the accurate clinical dosimetry is essential for the effective radiation treatment, the desired patient outcome cannot be achieved without the adequate quality of clinical, physical and technical processes. A comprehensive IAEA audit methodology called the Quality Assurance Team for Radiation Oncology (QUATRO) was developed to review the entire radiotherapy chain and infrastructure. Since 2005 QUATRO audits have been conducted in approximately 90 radiotherapy centres in various world regions. The experiences above demonstrate that quality audits improve dosimetry and clinical practices. Audits have been effective in identifying discrepancies in dosimetry and in providing support to participating centres in resolving them. Audits can lessen the likelihood of major dosimetry errors and the resulting consequences for patient outcomes. Audits also address smaller errors and help in reducing uncertainties in the dose delivery thus improving the treatment quality for many patients. Audits can provide support and confidence when introducing new technologies and complex processes in radiotherapy. Audits verify the consistency of dosimetry practices among centres in different countries and world regions. They strengthen the confidence in clinical dosimetry both for physicists and clinicians who obtain assurance that their patients are given accurate doses in accordance with medical prescription. The significance of quality audits in radiotherapy and their impact on dosimetry and clinical practices have been widely recognized. Still, a large number of radiotherapy centres do not participate in such audit programmes. Due to obvious benefits, all centres should be encouraged to take part in quality audits in radiotherapy.

SP-0193 Quality improvement in radiotherapy: history, significance and impact of dosimetry audits J. Izewska 1 1 IAEA - International Atomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Vienna, Austria The concept of verification of radiation doses in medical applications was introduced in early 20th century, not long after radiation started to be used for treating cancer. Initially, to estimate the adequate daily fraction of radiation to be given to patients physicians exposed the skin of their own arms to radiation to produce the ‘erythema dose’. Since then, the methodologies, dose measurement tools and radiation therapy equipment have made a great progress. In 1925 R. Sievert established a circulating physical department for standardizing the Roentgen radiation used in cancer therapy in Sweden. The department found some unreliable dose meters and identified the need for better protective equipment. At the same time, the measurements of percentage depth doses collected during the visits were used as a reference dataset for the Roentgen facilities in Sweden. Another example of early dosimetry audits was documented in Poland; following the idea by Marie Curie, the Measurement Laboratory was established in 1936 for radiation dose measurements at Polish hospitals using radium and X-ray beams. The Dosimetry Laboratory of the International Atomic Energy Agency (IAEA) was set up in early 1960s with the aim of the provision of dosimetry audits for radiotherapy centres worldwide and for ensuring international consistency in radiation dosimetry. First trial inter- hospital comparisons were implemented by the IAEA in 1965–1966. In parallel, dosimetry comparisons of Co-60 and high energy beams from early medical accelerators were conducted among hospitals of France, Sweden, and in other countries. In USA, the Radiological Physics Center was established in 1968 to operate as an independent quality assurance office for multi-institutional cooperative group clinical trials. Since 1969, the calibration of radiotherapy beams in 2200 hospitals in 132 countries has been verified by the IAEA jointly with the World Health Organization (WHO) through postal dosimetry audits. One important part of the auditing process is related to resolving dosimetry discrepancies occurring in the audit; errors are traced, analysed and corrected. In early years, only approximately 50% audited centres had the acceptable beam calibration. Over the time, several radiotherapy centres improved