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The Correlations Between Treatment Response and Changes in Primary Tumor Volume and CT Number Using CBCT Image

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C Ma

C Ma1*, (1) Shandong Cancer Hospital and Institute, Jinan, Shandong Province


MO-RAM-GePD-J(B)-2 (Monday, July 31, 2017) 9:30 AM - 10:00 AM Room: Joint Imaging-Therapy ePoster Lounge - B

Purpose: To investigate the correlations between treatment response and changes in primary tumor volume (TV) and CT number (CTN) using kilovoltage cone-beam computed tomography (KV-CBCT).

Methods: Patients with inoperable and locally advanced NSCLC who received CRT and had daily CBCT during radiotherapy course were involved in this study. The contours of TV were manually delineated by radiation oncologists from CBCT images on days 1, 6, 11, 16, 21, 26, 32. The changes of TV and the mean CTN during the course of radiotherapy delivery were analyzed and correlated with clinical outcomes.

Results: CTN reduction was observed in primary tumors for all 54 patients from Day 1 (D1) to Day 32 (D32) CBCTs with a mean value of 24.91±12.34 Hu,and the TV reduced with a median shrinkage ratio of 28.28 (range, -15.57% - 61.67%) over the radiotherapy course. The change of CTN was linearly correlated with radiation doses (mean R2=0.889 ± 0.164), while the correlation between CTN changes and TV reduction ratio was weak with R2= 0.257. The ROC curve illustrated that both of CTN change (p=0.037) and TV shrinkage ratio (p=0.016) could predict treatment response and the area under the curve for combination of them was larger than any parameter alone (p=0.002). For patients with response, the CTN and TV change ratio were reduced by 28.44±13.12 Hu and 32.01% (range,8.46%-61.67%), which were significantly higher than those in the non-response patients with 19.63±8.67 Hu and 23.20% (range, -15.57%-38%) (p=0.005 and p=0.026), respectively.

Conclusion: The lung tumor CTN change was linearly correlated with radiation dose received. The changes of CTN and TV obtained from CBCT images had the potential to be early predictors of response.

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