ESTRO 2022 - Abstract Book

S756

Abstract book

ESTRO 2022

treatment journey allowing their individual needs to be met in a personalised manner. After completion of their cancer treatment patients will have a nurse-led discussion of treatment side-effects, a holistic needs assessment, education regarding detecting the signs and symptoms of recurrence, rapid access contact for advice and clinic as well as access to psychological support services. Patients will also receive annual mammograms as part of their patient-led follow-up. In this debate the evidence for patient-led follow-up will be discussed as well as arguments against regular hospital visits and regular investigations.

SP-0851 For the motion (rebuttal)

P. Franco

Italy Abstract not available

SP-0852 Against the motion (rebuttal)

O. Kaidar-Person 1

1 Sheba Tel Hashomer, Oncology Institute, Radiation Oncology, Ramat Gan, Israel

Abstract Text

The most important element in early breast cancer patient follow-up is to detect recurrences and adverse effects of treatment at a time point when intervention leads to a clinically significant outcome for the patient. The delicate balance, between required versus over-surveillance that may lead to unnecessary burden for the patient and the health system should be considered. In this debate we discuss the evidence for follow up of high-risk breast cancer patients, and how intensive follow-up might not necessarily lead to a better outcome.

Symposium: Challenging the traditional margins for microscopic diseases

SP-0854 Biological paths for spread of microscopic disease

E. Troost 1

1 Faculty of Medicine and University Hospital Carl Gustav Carus, Radiotherapy and Radiation Oncology, Dresden, Germany

Abstract Text The microscopic tumour extension, encompassed in the clinical target volume (CTV), has been extracted from relatively small series of thoroughly investigated tumour resection specimen. As a rule of thumb, depending on the tumour site and the underlying histology, the CTV may range from 5 mm up to 2-3 cm. In times when the identical radiation treatment plan was delivered throughout the entire course of treatment, this CTV concept may have been adequate. However, with the ever increasing capabilities of anatomical and functional tumour response assessment during treatment, treatment plan adaptation is mainstream nowadays. Moreover, highly conformal photon and in particular particle treatment plans, the latter exploiting the steep dose gradients, are offered to patients in order to reduce the normal tissue complication probability. In these situations, the gross tumour volume (GTV) is derived from the per-treatment imaging and the margins for the planning target volume (PTV) are maintained. However, the behaviour of the microscopic tumour extension and thus the CTV is entirely unclear. In this presentation, I will highlight the current status of the CTV as well as research projects aimed at unravelling the possible biological rationale for adapting the CTV during the course of treatment.

SP-0855 Deep learning and tumor growth modeling for identification of microscopic infiltration in GBM

J.C. Peeken 1

1 Klinikum rechts der Isar, Technical University of Munich, Department of Radiation Oncology, Munich, Germany

Abstract Text Clinical target volume (CTV) definition for adjuvant radiotherapy of glioblastomas (GBM) is commonly performed via isotropic expansion of the resection cavity and the residual gross tumor volume (GTV) or the FLAIR hyperintense region following international guidelines. A commonly used isotropic expansion of 2 centimeters is loosely based on postmortem analyses and imaging studies demonstrating that GBM recurrences occur within this distance in approximately 70-90% of cases (1–8). The efficacy of adjuvant radiotherapy proves that this approach covers a significant part of areas with microscopic tumor infiltration. On a patient-specific basis, one study showed that expansions ranging from one to three centimeters would have covered all individual locoregional recurrences. GBM growth, however, appears to be anisotropic as it is confined by anatomical barriers and happens with differing growth speeds in white and grey matter. Spatial localization of areas with microscopic infiltrations could thus be used to generate more individualized CTVs. This talk summarizes two promising solutions for the improved definition of a microscopic tumor volume using medical imaging