Room: Exhibit Hall | Forum 6
Purpose: To investigate the correlations between primary tumor volume (TV) variations and physical density changes by kilovoltage cone-beam computed tomography (KV-CBCT). The second aim is to assess whether these could be valuable to predict chemoradiation therapy (CRT) response in non-small cell lung cancer (NSCLC) patients.
Methods: Fifty-four patients with inoperable and locally advanced NSCLC who received CRT and CBCT were involved in this study. Primary tumor were manually delineated on CBCT images on 1st, 5th, 10th, 15th, 20th, 25th, and 30th fractions through in-house software. TV and CT numbers (CTN) were measured on each of the seven observation points by IBEX. Variation ratios of TV (cmÂ³) and CTN mean values (HU) during the treatment course were analyzed and correlated with clinical outcomes evaluated by RECIST criteria.
Results: All patients had various degrees of changes in CTN and TV during radiation delivery. The change of CTN was linearly correlated with radiation doses (mean RÂ²=0.879Â±0.164), while the correlation between CTN changes and TV reduction ratio was weaker (RÂ²=0.343). For patients with response, the TV and CTN reduced by 32.01% (8.46%-61.67%) and 28.44Â±13.12 Hu, which were significantly higher than those in the non-response patients with 23.20% (-15.57%-38%) and 19.63Â±8.67 Hu (p=0.048 and p=0.0016), respectively. ROC curve illustrated that both TV shrinkage ratio (AUC=0.693, p=0.016) and CTN variation (AUC=0.666, p=0.037) could predict treatment response. The area under curve for combination of TV and CTN was larger than any one alone (AUC=0.751, p=0.002). TV reduction during the period of F5-F10 (AUC=0.667, p=0.036) and CTN changes between F10 and F15 (AUC=0.753, p=0.002) demonstrated significance difference between response and non-response.
Conclusion: For NSCLC tumor target, CTN variation was linearly correlated with the radiation dose received. TThe changes in CTN and TV obtained from CBCT images have the potential capability to predict an early response of NSCLC.
Cone-beam CT, Radiation Therapy