Association of Computed Tomography Morphologic Criteria With Pathologic Response and Survival in Patients Treated With Bevacizumab for Colorectal Liver Metastases

Abstract

HE ADDITION OF BEVACIZUMAB, a monoclonal antibody against vascular endothelial growth factor, to cytotoxic chemotherapy is associated with improved survival in patients with stage IV colorectal cancer and higher pathologic response rates in patients undergoing resection of colorectal liver metastases. 1,2 Response to bevacizumab, which exerts an antiangiogenic mechanism of action, may be inadequately assessed by traditional size-based radiologic criteria, the Response Evaluation Criteria in Solid Tumors (RECIST), which were designed for assessing tumor volume reduction following cytotoxic chemotherapy. [3][4][5] In support of this, a recent phase 3 trial showed that the addition of bevacizumab to oxaliplatin-based chemotherapy for metastatic colorectal cancer improved progression-free survival without affecting RECIST-defined response rates. 6 Recently, pathologic response to preoperative chemotherapy has been shown to correlate with improved sur-Author Affiliations are listed at the end of this article.

Postchemotherapy histological analysis of major intrahepatic vessels for reversal of attachment or invasion by colorectal liver metastases

“…Further, RECIST criteria may have limited ability to assess response to such biological agents. 10 After regimens including bevacizumab, optimal response according to imaging was defined as a change in metastases from lesions with heterogeneous attenuation and thick, irregular borders to bland, homogeneously hypodense masses with a sharp interface between tumors and adjacent liver parenchyma. Homogeneous attenuation shown by metastases responding to bevacizumab in combination regimens likely reflects replacement of treated tumor by fibrous connective tissue.…”

Colorectal Liver Metastases

“…Morphologic change in a treated metastasis may better reflect tumor response. 9 When tumors change from heterogeneous consistency and irregular borders to homogenous density, clearly demarcated borders, and no enhancement, this pattern strongly correlates with pathologic response, margin control, and survival.…”

Evaluation of response after SBRT for liver tumors

“…Price et al 16 Liver primary tumors Jarraya et al began in 2013 by describing post-therapeutic CT transformations of secondary hepatic lesions treated with cyberknife. 35 Following the example of the work by Chun on the hepatic metastases treated by bevacizumab, 8 they described four types of responses according to the evolution in size, the occurrence of a lobulated enhancement or total necrosis. According to that work, the use of RECIST criteria may be inadequate.…”

“…7 The enhancement of hepatic metastases due to colorectal cancer after treatment with bevacizumab has also been taken into account from 2009. 8 Positron-emission tomography (PET) is a functional imaging modality that logically claims to best evaluate the liver treated by SBRT. Considering the limitations of anatomic imaging alone in assessing the activity of newer cancer therapies that stabilize disease, 18F-FDG PET could be efficient in such cases.…”