Prediction of Early Response to Chemoradiation Therapy in Non–Small Cell Lung Cancer by Using Cone Beam Computed Tomography–Based Tumor Volume and Density Changes

Abstract

Response evaluation is critical in assessing effectiveness of anti-cancer treatment; however, the Response Evaluation Criteria in Solid Tumor (RECIST) may underestimate the efficacy of non–small cell lung cancer (NSCLC) treatment. We sought 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) to assess whether these could be valuable in predicting chemoradiation therapy (CRT) response in NSCLC patients. Patients with inoperable and locally advanced NSCLC who received CRT and had daily CBCT during the course of radiation therapy were involved in this study. The contours of TV were manually delineated by the radiation oncologist from CBCT images on days 1, 6, 11, 16, 21, 26, and 32. The changes in TV (cm3) and the mean CTN (Hu, Hounsfield Units) during the course of radiation therapy delivery were analyzed and correlated with clinical outcomes, based on a clinical examination and serial CT scans. A computer software was used to perform Pearson and t-test analysis of the data, and logistic regression was applied to assess prediction abilities of CTN and TV. CTN reduction was observed in primary tumors for all 56 patients from Day 1 (D1) to Day 32 (D32) CBCTs with a mean value of 24.91±12.34 Hu, and the TV reduced by 30.11 ±23.80 cm3. The lung tumor CTN change was linearly correlated with radiation dose received. The changes in CTN and TV obtained from CBCT images had the potential to be early predictors of response, which could identify NSCLC patients who can benefit from CRT. Prediction value could be improved by a combination of the CTN and TV changes.