ESTRO 2022 - Abstract Book

S385

Abstract book

ESTRO 2022

Conclusion Treatment arms in our randomized trial of high-dose versus standard dose twice-daily TRT in LS SCLC were well balanced with respect to both volumes of PTV and treatment planning techniques.

OC-0441 Risk of cardiac death increases with dose to cardiac sub structure avoidance region in lung cancer

A. Abravan 1 , C. Faivre-Finn 1 , K. Banfill 1 , A. Mcwilliam 1 , M. van Herk 1

1 The University of Manchester, Division of cancer sciences, MANCHESTER, United Kingdom

Purpose or Objective There is emerging evidence that radiotherapy (RT) dose to cardiac substructures, specifically those located at the base of the heart, is associated with cardiac events and worse overall survival in lung cancer patients. Darby et al reported a linear relationship between excess major cardiac events and mean heart dose in patients with breast cancer. We investigated if a similar relationship exists for lung cancer patients treated with curative-intent RT, considering heart substructures dose. Materials and Methods 2488 lung cancer patients treated between 2010-2016 at a single institute with radical RT (55/60-66Gy in 20/30-33 fractions) with or without chemotherapy were included. Primary endpoint was cardiac death (CD) occurring after day 1 of RT. Cause of death recorded on death certificates was categorised using WHO-ICD10 codes from Public Health England data. Pre-existing cardiac disease (PCD) prior to RT was collected from Hospital Episode Statistics data. For each patient, the planning CT scan was deformably registered (using NiftyReg non-rigid registration) to 6 template patients with a cardiac avoidance region (CAR) segmented by a radiation oncologist. CAR was defined in consensus with a cardiologist based on previous studies and included superior vena cava, right atrium, aortic root, and proximal segments of the coronary arteries. Mean CAR dose was calculated for all patients and averaged over the 6 sets. A nested case-control design was used, with cases being patients who died with a cardiac cause. Each case was matched with three controls according to age range, gender, PCD, tumor volume quartile, RT, and chemotherapy regimen. Rate ratios for CD were estimated with the use of conditional logistic regression after stratification. The rate of CD was modelled as bx, where x was the EQD2( α / β =3) dose to CAR (in Gy) and b (slope) was the percentage increase in the rate CD per Gy. Results 709 (28%) had PCD and 289 (12%) of the patients died with a cardiac cause. Median of the mean EQD2 dose to CAR was 9.9 Gy (range, 0.5-61.5) and 10.8 Gy (range, 0.5-58.7) for patients with and without PCD, respectively. The rate of CD increased