Association of computed tomography morphologic criteria with pathologic response and survival in patients treated with bevacizumab for colorectal liver metastases.

Context The standard criteria used to evaluate tumor response, the Response Evaluation Criteria in Solid Tumors (RECIST), were developed to assess tumor shrinkage after cytotoxic chemotherapy and may be limited in assessing response to biologic agents, which have a cytostatic mechanism of action. Objective To validate novel tumor response criteria based on morphologic changes observed on computed tomography (CT) in patients with colorectal liver metastases treated with bevacizumab-containing chemotherapy regimens. Design, Setting, and Patients A total of 234 colorectal liver metastases were analyzed from 50 patients who underwent hepatic resection after preoperative chemotherapy that included bevacizumab at a comprehensive US cancer center from 2004 to 2007; date of last follow-up was March 2008. All patients underwent routine contrast-enhanced CT at the start and end of preoperative therapy. Three blinded, independent radiologists evaluated images for morphologic response, based on metastases changing from heterogeneous masses with ill-defined margins into homogeneous hypoattenuating lesions with sharp borders. These criteria were validated with a separate cohort of 82 patients with unresectable colorectal liver metastases treated with bevacizumab-containing chemotherapy. Main Outcome Measures Response determined using morphologic criteria and RECIST was correlated with pathologic response in resected liver specimens and with patient survival. Results Interobserver agreement for scoring morphologic changes was good among 3 radiologists (κ, 0.68-0.78; 95% confidence interval [CI], 0.51-0.93). In resected tumor specimens, the median (interquartile range [IQR]) percentages of residual tumor cells for optimal morphologic response was 20% (10%-30%); for incomplete response, 50% (30%-60%); and no response, 70% (60%-70%; P  Conclusion Among patients with colorectal liver metastases treated with bevacizumab-containing chemotherapy, CT-based morphologic criteria had a statistically significant association with pathologic response and overall survival.