Determining the Ideal Time for Implementing Adaptive Radiation Therapy in the Treatment of Non-Small Cell Lung Cancer through the Analysis of Cone-Beam Computed Tomography Images

Abstract

Radiotherapy (RT) has an important role in the management of locally advanced non-small cell lung cancer (LA-NSCLC) but is also challenging due to treatment uncertainties. Adaptive radiation therapy (ART) is a possible solution that is widely used but varied with limited consensus. Cone beam computed tomography (CBCT) is frequently used during the treatment process to confirm the accuracy of the treatment location and the changes in the tumor during treatment can be observed also from CBCT images. We collected the characteristics of patients and analysis the changes of tumor volumes from weekly CBCT images and try to predict the optimal timing for ART in modern RT. LA-NSCLC patients treated with definitive chemo-radiotherapy by volumetric modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) were enrolled in this study. CBCT images during treatment in the second, fourth, and sixth weeks were collected and the region of interest (ROI) was contoured by the same experienced radiation physician. The image segmentation and processing were done using a programming environment. The change in tumor volume during mid-treatment and at the end of treatment were calculated and the regression analysis was used to evaluate the correlation of tumor volume changes during treatment course. Since 2018 to 2021, total 20 LA-NSCLC patients treated with definitive chemo-radiotherapy (CCRT) were enrolled in this study. There are 17 males and 3 females, respectively with an average age of 67 years. All patients received chemotherapy and a radiation therapy prescriptive dose of 60 Gy in 30 fractions to a planning target volume (PTV). Totally 1,760 image slices were analyzed. The average tumor volume before treatment in patients who underwent ART or without ART was 273.84 cm3 and 132.84 cm3 respectively. The median tumor volume changes were 15.04%, 35.68%, and 55.37% at 2,4, and 6 weeks, respectively. Patients who achieved a tumor volume reduction of more than 40% in the fourth week had a better final tumor reduction outcome than those who did not meet this volume reduction goal. However, no significant difference was found in the change in tumor volume from the fourth to the sixth week. This study suggests that monitoring tumor volume changes during the first half of treatment using CBCT images may be an effective way to predict the final tumor reduction outcome in patients with LA-NSCLC undergoing adaptive radiation therapy (ART) in a modern CCRT treatment setting. Specifically, the study found that a tumor volume reduction of more than 40% in the fourth week may predict a better final tumor reduction outcome. Based on this finding, the study suggests that redesigning the treatment plan based on the change in tumor volume during the first half of treatment may improve the final tumor reduction effect in patients with NSCLC undergoing ART.