Objective: To assess the effect of bevacizumab on tumor vessels, and the reversibility of the effect, using contrast-enhanced ultrasonography (CEUS) and histology in patients with metastatic liver tumors derived from colorectal cancer.

Background Data: Direct evidence on the reversibility of any change in tumor vascularity upon bevacizumab cessation in the clinical setting is lacking.

Methods: The study included 10 patients who received chemotherapy including bevacizumab, experienced a reduction in tumor vascularity as demonstrated by CEUS and consequently underwent liver resection. CEUS was performed before and immediately after 4 courses of chemotherapy and one day before surgery. The number of microvessels highlighted by anti-CD34 antibody in the viable tumor tissue was counted to quantify the microvessel density (MVD). As a control, 10 surgical specimens from 10 patients who had not received chemotherapy were examined.

Inclusion Criteria:

• patients who received chemotherapy (FOLFOX) including bevacizumab. The patients had an associated reduction in tumor vascularity as estimated by ultrasonography and consequently underwent surgical resection of the metastatic liver tumors for curative purposes.

Exclusion Criteria:

• none

Residents cared by the institution this study was perfomed.