Abstract
The correlations between early responses and the variations in physical density and primary tumor volume (TV) according to cone-beam computed tomography (CBCT) during chemoradiotherapy for non-small cell lung cancer (NSCLC) patients were investigated. 54 patients with inoperable and locally advanced NSCLC were included in this study. The CT numbers (CTN) and TV were measured on each of the seven observation points. The changes in the mean CTN values and the variation ratios of TV during the treatment course were analysed and correlated with the clinical outcomes, as evaluated by the RECIST criteria. For patients who responded to treatment, the CTN and TV change ratio decreased by 28.44 ± 13.12 HU and 32.01% (range, 8.46–61.67%); these values were significantly higher than those in the non-responding patients, with 19.63 ± 8.67 HU and 23.20% (range, −15.57–38%) (p = 0.016, p = 0.048), respectively. The area under curve for the combination of CTN and TV was larger than either alone (AUC = 0.751, p = 0.002). The differences between response and non-response were most significant between Fraction 10 and Fraction 15 for CTN changes and between Fraction 5 and Fraction 10 for the TV regression ratio. The changes in CTN and TV obtained from CBCT images have the potential capability to predict an early response of NSCLC.
Highlights
Non-small cell lung cancer (NSCLC) is the main subtype of lung cancer and accounts for 80% of all lung cancers
The mean computed tomography (CT) number (CTN) exacted from the first cone-beam computed tomography (CBCT) was 63.21 ± 28.93 HU, and the mean CTN extracted from last CBCT was 38.29 ± 19.91 HU
Among the 54 cases, 61.1% of patients decreased at least 20 HU, and 12 patients’ CTN reduction fluctuated by approximately 10 (10 ± 5) HU
Summary
Non-small cell lung cancer (NSCLC) is the main subtype of lung cancer and accounts for 80% of all lung cancers. Changes in the longest axis of targeted lesion is the main evaluation criterion in RECIST, which ignores changes in other forms to a certain extent, such as the short axis and tumor volume[7,8] These morphologic changes based on uni-dimensional measurements neglect the molecular changes and cannot effectively reflect biologic alternations in tumors, which may lead to inaccurate predictions of treatment response. As part of image-guided radiation therapy (IGRT), kilovoltage cone-beam computed tomography (KV-CBCT) could provide the capability to monitor the tumor density changes and volume regression during the course of chemoradiotherapy. This study proposed to investigate the correlations between chemoradiation treatment response and variations in primary CTN and TV by KV-CBCT in NSCLC patients and to determine the appropriate time points for prediction
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