ESTRO 2024 - Abstract Book

S5051

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

1. Paradis KC, Mayo C, Owen D, et al. The Special Medical Physics Consult Process for Reirradiation Patients. Adv Radiat Oncol 2019;4:559-65.

2. De Ruysscher D, Faivre-Finn C, Le Pechoux C, Peeters S, Belderbos J. High-dose re-irradiation following radical radiotherapy for non-small-cell lung cancer. Lancet Oncol 2014;15:e620-e4.

3. Rulach R, Ball D, Chua KLM, et al. An International Expert Survey on the Indications and Practice of Radical Thoracic Reirradiation for Non-Small Cell Lung Cancer. Adv Radiat Oncol 2021;6:100653.

1480

Poster Discussion

Dose-response of oesophageal toxicity after thoracic re-irradiation with or without chemotherapy

Robert Rulach 1,2 , Stephen Harrow 3 , Anthony Chalmers 2 , John Fenwick 4

1 Oxford University Hospitals NHS Trust, Oncology, Oxford, United Kingdom. 2 University of Glasgow, Oncology, Glasgow, United Kingdom. 3 NHS Lothian, Oncology, Edinburgh, United Kingdom. 4 University College London, Oncology, London, United Kingdom

Purpose/Objective:

Re-irradiation for non-small cell lung cancer is associated with median survival of 17 months, with a mean risk of grade 3 (G3) oesophagitis of 2% (range 0-9%) 1 . Current re-irradiation dose constraints for the oesophagus are consensus-based, formed from clinical experience and limited data. Guidelines suggest limiting the cumulative maximum dose (cDmax) to the oesophagus to between 75 and 110Gy equivalent dose in 2-Gray fractions (EQD2) 2 . We aimed to develop a re-irradiation dose/toxicity model to predict the rate of toxicity at a given cDmax. This would allow for better counselling of patients regarding the potential risks of re-irradiation and refinement of cumulative dose constraints.

Material/Methods:

We performed a MEDLINE literature search for studies published between 01/01/1970 and 01/10/2018 that reported the cDmax received by the oesophagus over two or more treatments and the associated ≥G3 toxicity. We also compiled data on inter-treatment interval and the use of concurrent chemotherapy (ConChT) with re-irradiation. We conducted logistic regression on the dataset using R (version 3.6.1, R core team, 2019). The models were used to identify the cDmax levels associated with pre-specified G3 toxicity rates of 5% and 20%. 95% confidence intervals (CI) were calculated using 2000 block bootstrapped samples. Assessment of model fit was performed by dividing the collected dataset into deciles and plotting modelled toxicity rates against the observed rates. Model performance was assessed using the Pearson correlation coefficient.

Results: