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SU‐F‐J‐67: Dosimetric Changes During Radiotherapy in Lung Cancer Patients with Atelectasis
Author(s) -
Guy C,
Weiss E,
Jan N,
Reshko L,
Christensen G,
Hugo G
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4955975
Subject(s) - medicine , atelectasis , nuclear medicine , radiation therapy , lung cancer , dosimetry , lung , lung volumes , radiology
Purpose: Large geometric changes which occur during thoracic radiotherapy alter normal anatomy and target position and may induce clinically important dose changes. This study investigates variation of organ‐at‐risk (OAR) dose caused by atelectasis resolution during radiotherapy. Methods: 3D IMRT treatment plans were obtained for 14 non‐small‐cell lung cancer patients. Dose of the clinical plan was recalculated on a baseline scan in which lung was collapsed and on a midtreatment scan in which lung re‐aeration had occurred. The changes in OAR doses were compared between the two time points. RTOG‐0617 and inhouse dose‐volume constraints were chosen for investigation and included spinal cord, esophagus, heart, and healthy lung. Results: 17 dose metrics were evaluated. The mean (SD) of change in mean lung dose, from baseline to mid‐treatment (average taken across all patients), was 0.2 Gy (2.2 Gy) and ranged from −3.2 Gy to 6.0 Gy. 50% of patients experienced relative changes in mean lung dose of greater than 5% of baseline value. The mean (SD) of changes in heart V 40 , V 45 , and V 60 were 3.2% (3.4%), 3.0% (2.9%), and 1.4% (2.1%), respectively, and were significant for the study cohort (Wilcoxon signed‐rank test, p=0.0107 for V 40 , p=0.0052 for V 45 , and p= 0.0353 for V 60 . Ranges in changes of Heart V 40 , V 45 , and V 60 were −1.9% to 8.6%, −1.7% to 7.5%, and −2.1% to 4.5%, respectively. The mean (SD) of changes in Esophagus PRV Dmean and V 60 were 0.3 Gy (3.3 Gy) and 0.8% (7.7%), respectively, and ranged from −4.8 Gy to 6.8 Gy for Dmean and −15.2% to 14.6% for V 60 . Conclusion: Patients with atelectasis present at the start of radiotherapy experience significant increases in heart dose. Substantial increases in mean lung dose also occur in a subset of patients. This work supported by the National Cancer Institute of National Institutes of Health under Award Number R01CA166119. Disclosures: Phillips Medical systems (Hugo, Weiss), National Institutes of Health (Hugo, Weiss, Christensen), and Roger Koch (Christensen) support, UpToDate (Weiss) royalties, and Varian Medical Systems (Hugo, Weiss) license. No potential conflicts of interest.