Abstract Perspective: Clinical and dosimetric predictors of radiation pneumonitis in early-stage lung cancer treated with Stereotactic Ablative Radiotherapy (SABR). – An analysis of UK’s largest cohort of lung SABR patients.

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Stereotactic Ablative Radiotherapy (SABR) is the standard treatment for early-stage lung cancer. Radiation pneumonitis (RP) is the commonest side effects after lung radiotherapy, which can cause short term or long-term morbidity and rarely mortality. Robust data regarding the predictors of RP in patients treated with SABR is lacking. In this study, we have tried to explore the clinical and dosimetric predictors of RP in UK’s largest cohort of early stage lung cancer patients treated with SABR. 1266 patients included in the analysis. Patient were treated according to UK SABR consortium guidelines.  Significant proportion of patients were elderly with multiple co-morbidities and poor performance status. Eighty-five (6.7%) patients developed symptomatic RP (grade ≥2) with only five (0.4%) developing grade 3 RP. Five percent of patients developed rib fractures but only 28% of these were symptomatic. Our analysis showed lower lobe tumour location; larger tumour size, PTV, mean lung dose, lung V20Gy, and V12.5Gy were significantly associated with symptomatic RP. ROC curve analysis showed optimal diagnostic threshold for tumour size, PTV, mean lung dose, V20 and V12.5; are 22.5mm, 27.15cc, 3.7Gy, 4.6%, and 9.5%. Our research can be a stepping-stone to guide development of new lung dose constraints for lung SABR.

– Study author Animesh Saha, MD