ESTRO 2023 - Abstract Book

S618

Monday 15 May 2023

ESTRO 2023

The new phantom position was imaged using the daily MR-scans and the plan was generated on the modified phantom using the adapt to shape procedure. This process was repeated for five fractions, while leaving the film in the phantom, leading to the accumulated measured dose on the film. Single fractions were also measured and calculated for comparison. Calculations were performed using the treatment planning system Monaco (v5.51.10). A 2D plane matching the film was extracted from the 3D dose grid. The relative dose of the measurements and calculations were compared. Results The single and accumulated fractions show good agreement for measured and calculated dose distributions and dose profiles. The dose distributions and differences of the dose profiles of the accumulated translation are illustrated in Figure 1.

The measurements and calculations were compared using a γ criteria of 2%/2mm. Threshold doses of 10% and 90% of the maximum dose were used. The original plan, accumulated translations, accumulated rotations and accumulated body modifications had a γ passing rate of 99.8%, 99.7%, 99.2%, 99.3% for 10% threshold dose and 99.6%, 99.4%, 95.5%, 99.2% for 90% threshold dose. The single fractions showed similar results, with γ passing rates ranging from 97.3% to 99.9% for all threshold doses. Except for one single fraction, with a γ passing rate of 93.9% and 83.0% for threshold doses of 10% and 90%. Conclusion The accumulated measurements and calculations show a good agreement for the dose distributions, dose profiles and γ passing rates. The multifraction treatments show similar dose differences and γ passing rates compared to single fraction treatments. OC-0752 The role of radiotherapy, surgery and chemotherapy in the cure of cancer. Is radiotherapy still 40%? T. Mee 1,2 , K. Kirkby 1,2 , N. Defourny 1,2 , N. Burnet 2 1 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom; 2 The Christie NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom Purpose or Objective The three major treatment modalities that play pivotal roles in cancer cure are surgery, radiotherapy (RT), and chemotherapy. Key research from 1992 by Tubiana estimated that 22% of cancer patients are cured predominantly by Proffered Papers: Health Services Research