Document Type : Original Paper
Faculty of Medicine, University of Paris-Saclay, 94276 Le Kremlin-Bicêtre, France. Department of Radiation Oncology, Tenon Hospital, 75020 Paris, France.
MATER Private Hospital, Physics department, Eccles Street, Dublin 7, Ireland.
Affidea, International Medical Centers, Center for Radiotherapy, 78000 Banja Luka, Bosnia and Herzegovina.
Faculty of Medicine, University of Paris-Saclay, 94276 Le Kremlin-Bicêtre, France.
Introduction: In this study, we aimed to evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marker motion in correlation with lung tumor motion and determine potential surrogate for respiratory gating radiation therapy (RGRT) depending on tumor localization, upper lobe (UL) versus lower lobe (LL).
Material and Methods: We included 58 patients (34 male and 24 female) with small lung cancer (≤ 5cm), who underwent stereotactic body radiation therapy (SBRT). All patients were scanned and contoured in all ten phases (Varian Eclipse 13.7) after four-dimensional computed tomography simulation (4D-CT). The motions of internal and external markers were analyzed and correlated with tumor motion. Pearson correlation coefficient (PCC) was used to evaluate the correlation between internal and external marker motion and tumor motion.
Results: The median (range) values of tumor motion were 3.2 (0.6-11.0) and 8.6 (4.0-24.0) mm in the UL and LL, respectively. The median (range) values of organs motion and PCC comparing UL vs. LL were 2.0 (0.3-9.1) vs. 6.0 (2.8-13.9) mm and 0.46 (0.30-0.95) vs. 0.79 (0.50-0.94) for the lung, respectively, 11.9 (2.5-16.3) vs. 12.5 (5.0-22.5) mm and 0.68 (0.11-0.93) vs. 0.89 (0.30-0.99) for the diaphragm, respectively, and 3.9 (2.5-6.3) vs. 7.6 (4.5-8.6) mm and 0.49 (0.20-0.70) vs. 0.59 (0.36-0.83) for the heart, respectively. The external marker motion and correlation coefficient for UL and LL were 2.5 (0.9-7.4) vs. 2.3 (1.0-5.9) mm and 0.54 (0.09-0.96) vs. 0.73 (0.27-0.94), respectively.
Conclusion: Lung and diaphragm motion correlate better with tumor motion than the external marker. Diaphragm motion can be an excellent indicator for treatment based on RGRT.