ESTRO 2024 - Abstract Book

S4987

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

Results:

Neither the coefficients for age nor healthy kidney volume were calculated to be significant for either A or B. The age range of patients in the cohort was small and so a very steep response would have been required. Mean BED was significantly related to A, the coefficient related to the asymptotic value of the eGFR was, βa3=-4.78 (-8.37 at 3% HDI and -1.32 at 97% HDI). For a patient with average age, kidney volume and healthy kidney dose in this cohort this equates to an approximate loss of 2-3% in eGFR, relative to baseline, per Gy mean BED after 18 months. The α/β ratio was assigned a uniform prior however the posterior notably favoured larger values of α/β. This supports the hypothesis that eGFR loss is a toxicity less sensitive to the number of fractions and so may not be altered much by a change in fractionation.

The results were not significantly affected by hyperparameter choices. The sampling was somewhat sensitive to very low values of the variance parameter for the gamma distributed priors.

Conclusion:

Hierarchical modelling provides a way for capturing the patient specific nature of A and B. The model is currently being evaluated and updated with a prospective cohort of patients to evaluate its utility in practice.

Keywords: SBRT, plan quality, local control

References:

[1] Siva S, Ali M, Correa RJ, Muacevic A, Ponsky L, Ellis RJ, Lo SS, Onishi H, Swaminath A, McLaughlin M, Morgan SC. 5 year outcomes after stereotactic ablative body radiotherapy for primary renal cell carcinoma: an individual patient data meta-analysis from IROCK (the International Radiosurgery Consortium of the Kidney). The Lancet Oncology. 2022 Dec 1;23(12):1508-16.