ESTRO 2023 - Abstract Book

S834

Tuesday 16 May 2023

ESTRO 2023

With increased life expectancy the number of elderly MIBC patients is expected to increase. Unfortunately elderly patients are often denied therapy. Existing guidelines on management of MIBC do not preclude curative treatments for elderly patients. However it is necessary to assess the risks and benefits of a treatment to avoid overtreatment that results in decreased health-related quality of life without prolonging survival. Materials and Methods In this presentation following questions will be addressed: 1) Do elderly patients have inferior survival, both cancer specific survival (CSS) and overall survival (OS), after curative therapy compared to younger patients with MIBC? 2) Do elderly patients have an increased complication rate after curative therapy compared to younger patients with MIBC? 3) Is there a place for radiotherapy in this population? Results A systematic review revealed that OS and CSS worsen significantly with age both after radical cystectomy and radiotherapy regimens. Except for perioperative mortality, morbidity seems comparable between younger and older patients. Ultrafractionated EBRT with 6 Gy fractions delivered once a week during 6 weeks to a total dose of 36 Gy recently showed to be well tolerated and associated with local control rates of 81.3% and can be considered a valuable alternative for the longer radiochemotherapy regimens, especially in an elderly population. Conclusion A proportion of elderly patients with MIBC will benefit from curative treatment. Primary radiotherapy is a valuable treatment option and alternative for radical surgery.

Teaching Lecture: Secondary malignancies from radiation - Is the prophecy fulfilled?

SP-0989 Secondary malignancies from radiation - Is the prophecy fulfilled? Y. Lawrence 1 1 Sheba Medical Center, Radiation Oncology, Tel HaShomer, Israel

Abstract Text Fear of inducing a radiation associated cancer is one of the great, yet often unmentioned, fears of both patients and their physicians. A historical overview of the topic will be presented, risk factors explained, and unanswered questions discussed. How frequent are such events? Is the mechanism fully understood? Twenty years ago it was predicted that the higher integral dose associated with IMRT treatments would lead to an increase in cases… has the prophecy been fulfilled?

Teaching Lecture: Status and recent developments in PET for adaptive radiotherapy

SP-0990 Status and recent developments in PET for adaptive radiotherapy E. Malinen 1 1 Oslo University Hospital, Department of Medical Physics, Oslo, Norway

Abstract Text Positron emission tomography (PET), nowadays mostly performed together with computed tomography (CT), has an established role in cancer diagnostics and radiotherapy (RT) planning. Using the workhorse 18F-fluorodeoxyglcucose (FDG) as tracer, pre-treatment PET scanning may provide crucial information on nodal status and tumor extension that will impact radiotherapy planning. In this regard, many studies have shown how the introduction of PET in the RT planning process has resulted in significant changes in the treatment plan. PET has also been the main imaging modality for dose painting, which is an approach to locally escalate the dose to the presumably most aggressive part of the tumor. In the current work, we will discuss the use of PET in adaptive RT (ART). Here, the hypothesis is that PET will reveal treatment-induced functional changes in the tumor and possibly normal tissues that can be used to modify the treatment plan, in the end leading to better outcomes. As patients respond differently to treatment, this may be seen as a form of individualized RT where both treatment volumes and/or dosages may become altered. The use of PET in ART has not been extensively investigated, and we will also discuss studies monitoring tumor and normal tissues by PET during the course of fractionated RT. In addition to tumor targeting, potential sparing of organs at risk such as bone marrow and salivary glands will be considered. We will present progress in deep learning algorithms and their role in tumor autodelineation and ART. The future potential of using other tracers than FDG such as Fibroblast Activation Protein Inhibitor (FAPI) will briefly be touched upon. Finally, we will discuss a technical innovation in the form of an integrated PET/CT-scanner and linear accelerator, which may facilitate biology-guided and online ART.

Teaching Lecture: MRI-only radiotherapy: Principles, challenges and future prospects

SP-0991 MRI-only radiotherapy: Principles, challenges and future prospects S. Klüter 1 1 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany

Abstract Text For many treatment indications in radiation oncology, it has become clinical standard to use additional MRI information for more accurate target delineation. MRI has may benefits, including superior soft tissue contrast and the possibility for additional functional imaging without any imaging dose exposure. It does not directly provide, however, the electron density information necessary for precise dose calculation.