ESTRO 2023 - Abstract Book

S64

Saturday 13 May

ESTRO 2023

0.003

Weight loss ITV volume

0.45 0.03 0.07 0.71 0.14 0.58 0.37

0.87 0.27 0.40 0.57 0.03

ITV amplitude

ITV amplitude change Diaphragm amplitude

Diaphragm amplitude change Diaphragm baseline shift

0.008

Air volume change 0.002 Table 1: Multivariate regression analysis factors and results. Bold text indicates significant variables. 0.21

Results A clear trend in an increase in heart dose was observed during treatment course, with linear regression showing an average increase in MHD compared to the planning CT of 0.51 [0.41,0.60] Gy/wk, and an average increase of 0.6 [0.3, 0.9] Gy on summed doses (Figure 2). Significant predictors of MHD changes are radiological depth of the heart in beam direction, heart volume changes, weight loss, diaphragm amplitude changes and baseline shift. Heart V40Gy was significantly predicted by number of beams, air volume changes inside the ITV, and ITV volume (Figure 2).

Conclusion A clear and clinically significant change in MHD was observed during IMPT treatments of esophagus. Heart position and volume related parameters, as well as weight loss and diaphragm position are factors influencing MHD. Based on this study, we believe that strict adaptation criteria are necessary, including monitoring of MHD, heart position and volume, weight loss, and diaphragm position. Additionally, V40Gy analysis suggests an increase of the number of beams to at least three would be beneficial, as well as strict monitoring criteria for air volume changes inside ITV. OC-0103 SCOPE2 PET: continuing CisCap v switch to CarPac in PET non-responders on dCRT for esophageal cancer S. Mukherjee 1 , C. Hurt 2 , S. Gwynne 3 , L. Nixon 2 , S. Bridges 2 , R. Adams 2 , G. Radhakrishna 4 , T. Maughan 5 , M. Hunter 2 , R. Kumar 2 , R. Roy 6 , C. Jones 7 , C. Marshall 8 , K. Bradley 8 , D. Callaghan 6 , S. Gollins 9 , H. Sheikh 4 , A. Bateman 10 , S. Falk 11 , B. Tranter 12 , G.J. Lewis 13 , E. Spezi 14 , M. Hawkins 15 , T. Crosby 16