Korean J Radiol.  2012 Dec;13(6):702-710. 10.3348/kjr.2012.13.6.702.

Dual-Energy CT in Patients Treated with Anti-Angiogenic Agents for Non-Small Cell Lung Cancer: New Method of Monitoring Tumor Response?

• Kim YN
• Lee HY
• Lee KS
• Seo JB
• Chung MJ
• Ahn MJ
• Park K
• Kim TS
• Yi CA

• KMID: 1397500
• DOI: http://doi.org/10.3348/kjr.2012.13.6.702

Abstract

OBJECTIVE
To evaluate tumor responses in patients treated with anti-angiogenic agents for non-small cell lung cancer (NSCLC) by assessing intratumoral changes using a dual-energy CT (DECT) (based on Choi's criteria) and to compare it to traditional Response Evaluation Criteria in Solid Tumors (RECIST) criteria.
MATERIALS AND METHODS
Ten NSCLC patients treated with bevacizumab underwent DECT. Tumor responses to anti-angiogenic therapy were assessed and compared with the baseline CT results using both RECIST (size changes only) and Choi's criteria (reflecting net tumor enhancement). Kappa statistics was used to evaluate agreements between tumor responses assessed by RECIST and Choi's criteria.
RESULTS
The weighted kappa value for the comparison of tumor responses between the RECIST and Choi's criteria was 0.72. Of 31 target lesions (21 solid nodules, 8 lymph nodes, and two ground-glass opacity nodules [GGNs]), five lesions (16%) showed discordant responses between RECIST and Choi's criteria. Iodine-enhanced images allowed for a distinction between tumor enhancement and hemorrhagic response (detected in 14% [4 of 29, excluding GGNs] of target lesions on virtual nonenhanced images).
CONCLUSION
DECT may serve as a useful tool for response evaluation after anti-angiogenic treatment in NSCLC patients by providing information on the net enhancement of target lesions without obtaining non-enhanced images.

Keyword

Targeted therapy; Tumor response assessment; Response criteria; Guideline; Non-small cell lung cancer; Dual energy CT

MeSH Terms

Adult
Aged
Angiogenesis Inhibitors/*therapeutic use
Antibodies, Monoclonal, Humanized/*therapeutic use
Carcinoma, Non-Small-Cell Lung/drug therapy/*radiography
Female
Humans
Image Processing, Computer-Assisted
Lung Neoplasms/drug therapy/*radiography
Male
Middle Aged
*Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Diagram of three-material decomposition of voxel used by dual-energy software. This software splits every voxel in 80- and 140-kV image pair into three components represented by air, soft tissue, and iodine (for ground-glass nodule) or fat, soft tissue, and iodine (for solid nodule or lymph node). (a), (b), (c), and (d) are fixed points of CT attenuation values from two different energies for air, fat, soft tissue, and iodine, respectively. Intercept x or y along iodine axis represents iodine content of voxel on this two-energy plot. Virtual unenhanced images display noniodine component of voxel, and iodine-enhanced images display z intercept (i.e., iodine content). CGN = ground-glass opacity nodule

• 

  Fig. 2 Hemorrhagic tumor response detected on dual-energy CT in 66-year-old man with lung adenocarcinoma. A. Previous baseline enhanced CT image shows 35 mm-sized primary tumor with net enhancement of 48 HU (subtraction of CT attenuation value on nonenhanced image from that of enhanced image; 68 minus 20 HU) in left lower lobe. B. Enhanced weighted-average image obtained from dual-energy CT after chemotherapy shows about 28% increase in size of primary tumor and also increased CT attenuation value (up to 82 HU, circular regional of interest [ROI]). Thus, tumor response was assessed as progressive disease on basis of traditional RECIST 1.1. C. In contrast, virtual nonenhanced image shows primary cancer CT attenuation value of 53 HU (circular ROI), suggesting hemorrhagic component (arrows). D, E. Color coded (D) and grayscale (E) iodine-enhanced images show tumor (arrows) attenuation value of 29 HU, declined value by 40% of net enhancement calculated from previous baseline chest CT. Therefore, tumor response was assessed as partial response by Choi's criteria based on dual-energy CT.

• 

  Fig. 3 New pulmonary metastases manifested as ground-glass opacity nodules (part solid) in 78-year-old woman with lung adenocarcinoma in right upper and lower lobes. A, B. Enhanced weighted-average image obtained from dual-energy CT shows newly developed 10-mm (A) and 12 mm-sized (B) ground-glass opacity nodules in right lung (arrows). Ground-glass opacity nodules are equivocal (not definitely defined) lesions on RECIST 1.1 version. Thus, tumor response was assessed as stable disease. C, D. These nodules shows substantial enhancement (58 HU in C and 89 HU in D) on color coded iodine-enhanced images obtained from dual-energy CT (arrows). Therefore, tumor response was assessed as progressive disease. E, F. Conventional images on further follow-up CT scans (two months after dual energy CT) show marked increase in nodule size with internal new cavitation (arrows), suggestive of cavitary metastases. Tumor response was again confirmed as progressive disease.

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