ESTRO 2025 - Abstract Book

S55

Invited Speaker

ESTRO 2025

4735

Speaker Abstracts Radiobiological comparison of different radiation qualities: Alpha vs beta vs external beam radiation Julie Nonnekens Molecular Genetics and Radiology & Nuclear Medicine, Erasmus MC, Rotterdam, Netherlands Abstract: Targeted radionuclide therapy (TRT) is an emerging radiation therapy modality that utilizes radioactively labeled molecules to selectively target tumor cells. Upon radioactive decay, the emitted radiation induces DNA damage, ultimately leading to cell death. Despite its growing clinical use, much of our radiobiological understanding of TRT has been extrapolated from external beam radiotherapy (EBRT) with X-rays, which differs fundamentally in its physical properties. EBRT is delivered at a high dose rate over a short duration, whereas TRT relies on the natural decay of radionuclides, resulting in continuous, lower-dose-rate radiation over extended periods (days to weeks). These differences significantly influence biological responses to radiation and vary depending on the radionuclide used. Clinically, beta-emitting radionuclides such as lutetium-177 and yttrium-90 are most commonly employed, but increasing evidence suggests that alpha-emitters like actinium-225 and Pb-212 exhibit higher efficacy due to their high linear energy transfer (LET) and increased DNA damage complexity.

In this presentation, I will compare the physical and radiobiological characteristics of EBRT and TRT with alpha and beta emitters, highlighting their impact on dose-effect relationships and therapeutic effectiveness.

4736

Speaker Abstracts Integration of prognostic factors and geriatric assessment into clinical decision-making Sandro V Porceddu Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Australia

Abstract:

More than half of all new cancer diagnoses occur in patients 65 years and older. Chronologic age provides minimal information regarding tolerance to cancer therapy. This is of particular importance given the significant toxicity associated with the management of locally advanced head and neck cancer. Understanding a patient’s biologic age through identification of pre-existing co-morbidities and organ-specific changes can provide greater insight into their ability to tolerate aggressive treatment. Frailty, as part of the aging process often results in limited reserves and can become obvious once physiologically challenged through cancer treatment. Identifying the frailer older patient is of paramount importance before embarking on curative standard of care. Important prognostic factors in determining fitness for therapy in the older patient include functional status (ability to perform daily tasks), performance status such as ECOG, co-morbidities, cognitive function, concurrent medications, nutritional status and psycho-social supports.