ESTRO 2024 - Abstract Book

S90 ESTRO 2024 in mechanisms will result in less side effects and greater efficaciousness. An ongoing ESMO-ESTRO project will facilitate this. Invited Speaker

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Radiobiological underpinnings to trials of re-irradiation: How can cohort studies help?

Dorota Gabrys

Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Radiotherapy, Gliwice, Poland

Abstract:

The diversity of re-irradiation practices in radiotherapy departments highlights the need for high-quality scientific evidence to guide treatment decisions and define safe limits on cumulative dose. Unfortunately, conducting a prospective randomized trial in the re-irradiation setting is extremely difficult since patient selection for re-irradiation remains challenging due to variability in recurrence character, trial recruitment may be extended over a long period of time, may be unethical, or some of the toxicities are difficult to report. In turn, we have a cohort study, which is a type of non-randomized study in which specific groups of people are followed over time to examine the effects of re-irradiation or other factors that may influence toxicity. A prospective follow-up cohort study collects participants and follows them over time. A retrospective cohort study identifies individuals who undergone re-irradiation and follows them from enrollment to the present. They can be performed in single center and then most studies are performed on small groups of patients, which limits a detailed summary of both the effects of re-treatment with radiotherapy and the complications that occur. They can be also conducted in the form of multi-institutional data collection, which significantly increases their value by enabling the collection of a larger group of patients who have undergone re-irradiation. In the cohort study, we analyse real patients who are treated by us during the clinical practice without any selections which means in all scenarios of recurrent tumours or secondary primary within a previously irradiated field. Therefore, the cohort studies evaluate outcomes and toxic effects after re-irradiation, which may help establishing new, potentially applicable dose constraints, and recommendations, provide knowledge about radiobiological factors, and identify prognostic subgroups. A cohort study can also serve as a validation set to test previously developed prognostic scores and their relevance for clinical practice. The lecture will present available cohort data and their potential significance for radiobiology.

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Radiobiology perspective

Neil G Burnet

Christie NHS Foundation Trust, Proton Beam Therapy Centre, Manchester, United Kingdom. MedAustron, Particle Therapy Centre, Vienna, Austria

Abstract:

Radiotherapy (RT) contributes significantly to 5-year survival. Overall, almost 40% of patients cured at 5 years have received RT and in those tumour sites where RT is delivered to >5% patients this figure is just over 50% (in