Jijo Paul1, Cungeng Yang1, Hui Wu2, An Tai1, Entesar Dalah3, Cheng Zheng4, Candice Johnstone1, Feng-Ming Kong5, Elizabeth Gore1, X Allen Li6. 1. Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin. 2. Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin; The Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou, China. 3. Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Medical Diagnostic Imaging, College of Health Science, University of Sharjah, UAE. 4. Biostatistics, Joseph. J. Zilber School of Public Health, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin. 5. Department of Radiation Oncology, Indiana University, Indianapolis, Indiana. 6. Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin. Electronic address: ali@mcw.edu.
Abstract
PURPOSE: To investigate early tumor and normal tissue responses during the course of radiation therapy (RT) for lung cancer using quantitative analysis of daily computed tomography (CT) scans. METHODS AND MATERIALS: Daily diagnostic-quality CT scans acquired using CT-on-rails during CT-guided RT for 20 lung cancer patients were quantitatively analyzed. On each daily CT set, the contours of the gross tumor volume (GTV) and lungs were generated and the radiation dose delivered was reconstructed. The changes in CT image intensity (Hounsfield unit [HU]) features in the GTV and the multiple normal lung tissue shells around the GTV were extracted from the daily CT scans. The associations between the changes in the mean HUs, GTV, accumulated dose during RT delivery, and patient survival rate were analyzed. RESULTS: During the RT course, radiation can induce substantial changes in the HU histogram features on the daily CT scans, with reductions in the GTV mean HUs (dH) observed in the range of 11 to 48 HU (median 30). The dH is statistically related to the accumulated GTV dose (R2 > 0.99) and correlates weakly with the change in GTV (R2 = 0.3481). Statistically significant increases in patient survival rates (P=.038) were observed for patients with a higher dH in the GTV. In the normal lung, the 4 regions proximal to the GTV showed statistically significant (P<.001) HU reductions from the first to last fraction. CONCLUSION: Quantitative analysis of the daily CT scans indicated that the mean HUs in lung tumor and surrounding normal tissue were reduced during RT delivery. This reduction was observed in the early phase of the treatment, is patient specific, and correlated with the delivered dose. A larger HU reduction in the GTV correlated significantly with greater patient survival. The changes in daily CT features, such as the mean HU, can be used for early assessment of the radiation response during RT delivery for lung cancer.
PURPOSE: To investigate early tumor and normal tissue responses during the course of radiation therapy (RT) for lung cancer using quantitative analysis of daily computed tomography (CT) scans. METHODS AND MATERIALS: Daily diagnostic-quality CT scans acquired using CT-on-rails during CT-guided RT for 20 lung cancerpatients were quantitatively analyzed. On each daily CT set, the contours of the gross tumor volume (GTV) and lungs were generated and the radiation dose delivered was reconstructed. The changes in CT image intensity (Hounsfield unit [HU]) features in the GTV and the multiple normal lung tissue shells around the GTV were extracted from the daily CT scans. The associations between the changes in the mean HUs, GTV, accumulated dose during RT delivery, and patient survival rate were analyzed. RESULTS: During the RT course, radiation can induce substantial changes in the HU histogram features on the daily CT scans, with reductions in the GTV mean HUs (dH) observed in the range of 11 to 48 HU (median 30). The dH is statistically related to the accumulated GTV dose (R2 > 0.99) and correlates weakly with the change in GTV (R2 = 0.3481). Statistically significant increases in patient survival rates (P=.038) were observed for patients with a higher dH in the GTV. In the normal lung, the 4 regions proximal to the GTV showed statistically significant (P<.001) HU reductions from the first to last fraction. CONCLUSION: Quantitative analysis of the daily CT scans indicated that the mean HUs in lung tumor and surrounding normal tissue were reduced during RT delivery. This reduction was observed in the early phase of the treatment, is patient specific, and correlated with the delivered dose. A larger HU reduction in the GTV correlated significantly with greater patient survival. The changes in daily CT features, such as the mean HU, can be used for early assessment of the radiation response during RT delivery for lung cancer.
Authors: Ke Nie; Hania Al-Hallaq; X Allen Li; Stanley H Benedict; Jason W Sohn; Jean M Moran; Yong Fan; Mi Huang; Michael V Knopp; Jeff M Michalski; James Monroe; Ceferino Obcemea; Christina I Tsien; Timothy Solberg; Jackie Wu; Ping Xia; Ying Xiao; Issam El Naqa Journal: Int J Radiat Oncol Biol Phys Date: 2019-01-31 Impact factor: 7.038
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