2353 - Dosimetric Evaluation of Radiotherapy Planning Optimization Based on Cardiac Subvolumes in Patients with Lung Cancer
Presenter(s)
D. Kisinma Azaklioglu1, H. F. Dincbas1, I. F. Demirel1, E. Demir1, H. C. C. Yildirim1, G. Can2, and S. Çavdar Karaçam3; 1Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Radiation Oncology, ISTANBUL, Istanbul, Turkey, 2Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Public Health, ISTANBUL, Istanbul, Turkey, 3Istanbul University-Cerrahpasa, Vocational School of Health Services, Radiotherapy Program, ISTANBUL, Istanbul, Turkey
Purpose/Objective(s): Definitive RT for locally advanced NSCLC, studies showed us that cardiac side effects decreases the survival rates, therefore heart doses gained importance. In this study, treatment plans of patients who had previously been planned in definitive doses compared dosimetrically with new plans that optimized doses to the cardiac subvolumes.
Materials/Methods: Planning CT images and plans of 40 locally advanced NSCLC patients who underwent curative radiotherapy in our clinic between 2018-2024 were reviewed. Cardiac subvolumes were contoured on previous planning CTs by a single senior physician. New plans were created to provide the highest possible level of protection of cardiac subvolumes by providing PTV coverage and standard dose constraints to OAR. Optimization was performed for cardiac subvolumes within the 50% isodose line, starting from priority 10 and not exceeding the PTV priority. Treatment plans for all patients were made using 6 MV photon energy and VMAT technique. The doses received by the cardiac subvolumes were compared between the original treatment plans and the newly generated plans. Paired t-test or Wilcoxon, Mann-Whitney U, and Spearman Correlation statistical methods were used in comparisons.
Results: Right and left atrium, right ventricle, left descending-right coronary, circumflex and pulmonary artery Dmean, and left descending artery Dmax doses were statistically significantly decreased in the new plans (Table 1). No significant decrease was observed in left ventricular Dmean and aortic Dmean doses. In left-sided tumors, the mean pulmonary artery dose could be reduced more than in right-sided tumors (23.66 Gy vs 12.16 Gy; p: 0.02). Minimal changes that would not disrupt the protocol were observed in PTV coverage (median 0.27% decrease), PTV maximum (median 0.22% increase), whole lung mean dose (median 0.53% increase), esophageal mean dose (median 0.81% increase) and spinal cord maximum dose (median 0.14% increase).
Conclusion: This study demonstrates that doses received by cardiac subvolumes can be reduced by specific optimization of cardiac subvolumes.
Abstract 2353 - Table 1| DOSES ORIGINAL PLAN(Gy) | DOSES OPTIMISED PLAN(Gy) | ||||||
| Median | 25.per | 75.per | Median | 25.per | 75.per | p | |
| R-atrium Dmean | 4.25 | 1.86 | 7.56 | 3.91 | 1.70 | 6.02 | .000*** |
| R-ventricul Dmean | 1.28 | .76 | 2.19 | 1.14 | .71 | 2.00 | .006** |
| L-ventricul Dmean | 1.70 | .90 | 3.41 | 1.58 | .85 | 3.03 | .166 |
| L-atrium Dmean | 10.46 | 3.67 | 14.74 | 8.04 | 3.43 | 13.19 | .000*** |
| LAD PRV V15(%) | .00 | .00 | 2.02 | .00 | .00 | 13.79 | .558 |
| LAD-Dmean | 13.80 | 5.34 | 24.23 | 11.36 | 4.27 | 19.10 | .000*** |
| LAD-Dmax | 23.99 | 10.37 | 50.19 | 16.06 | 7.60 | 30.78 | .000*** |
| LAD- V15 (%) | .00 | .00 | 43.71 | .00 | .00 | 28.49 | .700 |
| Cx-Dmean | 11.05 | 5.46 | 25.74 | 10.55 | 5.04 | 22.56 | .000*** |
| Cx-V15 (%) | .00 | .00 | 100.00 | .00 | .00 | 47.07 | .059 |
| RCA-V15 (%) | .00 | .00 | .00 | .00 | .00 | .00 | .281 |
| RCA-Dmean | 3.70 | 2.14 | 10.44 | 3.26 | 1.89 | 9.72 | .003** |
| Aort- Dmean | .00 | .00 | 9.48 | .00 | .00 | 9.05 | .709 |
| PA-Dmean | 19.31 | 11.11 | 27.93 | 16.45 | 8.00 | 22.85 | .000*** |