ESTRO 2022 - Abstract Book

S1642

Abstract book

ESTRO 2022

This preliminary study suggests that the estimation of bowel and rectum mean D50% dose from PoD selection can be easily calculated and validated against the TPS. Future work should include the exploration of the relationship between the CTAE toxifies in a larger dataset, apply this learning to other volumes or dose constraints could be more favorable to individualising the patients care pathway.

PO-1850 From children to superheroes in protontherapy, the RTT as sidekick

J. Claes 1 , H. Sels 2 , D. Callens 2

1 UZ Leuven, Radiation Therapy , Leuven, Belgium; 2 UZ Leuven, Radiation Therapy, Leuven, Belgium

Purpose or Objective Since June 2020 patients are treated with protontherapy (PT) in Particle at the University Hospital Leuven. In total 55 patients were treated. 53% of these patients are aged 0-18 year, 38% is under 12. Overall treatment time within PT is longer compared with photontherapy. Patients in PT need to lay still for up to 75 minutes. Immobilization material has its limits, so for children we can treat them under anesthesia (ANE) . ANE has crucial disadvantages. First of all, the children need to be sober. Oncological treatments can be demanding, therefore any weight loss must be avoided. Furthermore the rhythm of day and night is disrupted. Next to this, there are organizational disadvantages because PT treatments under ANE take more time. Various interventions were set up to reduce the use of ANE. Materials and Methods Interventions were created by the RTT’s of the PT department. Using unstructured observational research method, the effect of the interventions on the child’s and parent’s behavior were listed. During simulation, we allow parents to be with their child. We also give the opportunity to choose a drawing to be decorated on the mask. A social worker supports the child before and after the simulation/treatment. The children are provided with a superhero outfit, a superhero doll and a miniature version in Lego of our own bunker. Before the start of treatment, children will have a guided tour at Particle. To make the children at ease, they can let their music play during the sessions. There’s the possibility to switch on ambient light, accompanied with a video. Besides we have a rewarding system. Children receive a sticker for every session. With 5 stickers, they may do a quest in search of the doll. With 10 stickers, they get a gift. After treatment, we take a polaroid picture of them. They can also enter the bunker while riding an electric car. We encourage children to take something from home like a teddy bear. Educational courses for new RTT’s are offered. Results Only 6 patients (10%) underwent ANE. These patients were younger than 6 years. For the children who underwent treatment without ANE, a benefit in emotional wellbeing seems to be present. Next to this the physical disadvantages of undergoing ANE were abstained. The parents of the child also benefit. Their stay in the hospital is shorter and their child looks happier. These are real-world observational data, so it’s obvious that this has drawbacks, like subjectivity of the observations. Moreover we cannot sufficiently demonstrate that there is a statistically significant difference between the inter/intrafraction variations in children with or without ANE. Future research is needed to investigate this, as well the effects of long-term use of ANE. Conclusion We believe RTT’s play a major part in reducing the use of anesthesia for children undergoing PT. Interventions can easily be set up. The patient-RTT relationship can be considered as a decisive key factor in a comfortable treatment without ANE. 1 ASST Monza, Department of Radiation Oncology, Monza, Italy; 2 University of Milan Bicocca, School of Medicine and Surgery, Monza, Italy; 3 ASST Monza, Medical Physics Department, Monza, Italy; 4 University of Milan, Department of Physics, Milan, Italy Purpose or Objective Accurate patient setup is essential for delivering radiation therapy (RT) in accordance with the treatment plan. Interfraction translational and rotational errors have been determined from daily kVCBCT to evaluate the accuracy of two different immobilization devices in both moderate and extreme hypofractionated prostate RT. Materials and Methods Daily CBCTs from 40 and 33 prostate cancer patients who underwent at a single institution moderate hypofractionated RT in 20 fractions with bended knees (BK) and extreme hypofractionated RT in 4 or 5 fractions with straight knees (SK), respectively, were retrospectively analysed and compared, amounting to 1180 analysed datasets. The two immobilization devices are shown in Figures 1 and 2. Systematic and random shift components were evaluated using a clipbox matching based on a grey-value algorithm and validated by experienced radiation oncologists and RTTs. For both patient populations, the mean value of the average deviations M, the group systematic error ∑ and the group random error σ were computed for translations and rotations on all axes, respectively. Additionally, a Wilcoxon Mann Whitney test was performed to assess statistical significance between results (p=0.05). PO-1851 Impact in setup accuracy of two different immobilization devices in prostate cancer radiotherapy. V. Pisoni 1,2 , D. Panizza 3,2 , P. Caricato 3,4 , V. Faccenda 3,4 , S. Trivellato 3 , S. Arcangeli 1,2