BACKGROUND: Standard treatment of colorectal cancer includes both cytostatic chemotherapy and targeted therapies. Bevacizumab, targeting the VEGF receptor, is one of the primary targeted therapies that achieve better response rate and survival rate as compared to combination chemotherapy. To the best of our knowledge, there is no established single marker that can be used as a predictive marker in bevacizumab therapy.

MATERIAL AND METHODS: We enrolled 24 patients with the diagnosis of metastatic colorectal cancer in our study. During the study, 2 blood samples were drawn from patients before the first cycle and after the sixth cycle of bevacizumab therapy. Serum levels of VEGF, ANG II, and NO were recorded.

RESULTS: While the change across VEGF levels was found to be a statistically significant decreasing trend (p=0.009), this decrease was not found to be correlated with treatment response and hypertension development. Additionally, no statistically significant difference was found in terms of NO and ANG II levels.

CONCLUSIONS: This study showed a significant decrease in serum VEGF, but failed to show a significant change in NO and ANG II levels during bevacizumab treatment. Although no significant correlation was found between the presence of hypertension and markers, most patients (83%) had an increase in their blood pressure. Our results suggest that dynamic monitoring of NO and ANG II, along with VEGF, may not be useful as predictive markers for bevacizumab treatment in colorectal cancer.

Keywords: Angiotensin II - diagnostic use, Colorectal Neoplasms, bevacizumab, Nitric Oxide - diagnostic use, Vascular Endothelial Growth Factors, Angiotensin II - blood, Antibodies, Monoclonal, Humanized - therapeutic use, Colorectal Neoplasms - pathology, Demography, Hypertension - etiology, Monitoring, Physiologic, Nitric Oxide - blood, Vascular Endothelial Growth Factor A - blood