[Significance of CEA to predict the effect of chemotherapy with bevacizumab]

Since chemotherapy with bevacizumab has become available for advanced colorectal cancer, its effectiveness has been reported. Generally, the RECIST guideline has been adopted to determine antitumor effects, however, several problems exist with the image analysis. The purpose of this study was to evaluate the significance of CEA to predict the effect of chemotherapy with bevacizumab.

Twenty-five patients with advanced colorectal cancer were given chemotherapy with bevacizumab since August 2007. Among them, 18 patients were evaluated for the antitumor effect according to the RECIST guideline and were enrolled in this study. The relation of CEA and antitumor effects, and the change of CEA in every patient were analyzed retrospectively.

Patients consisted of 16 men and 2 women, with a mean age of 64. 2 (49-78) years. Chemotherapy with bevacizumab was given for 7 cases with metachronous recurrences after curative operations (6 cases with liver and/or lung metastasis and 1 case with pelvic recurrence), and for 11 cases with synchronous liver and/or lung metastasis. First-line chemotherapy was given to 16 cases and second-line to 2 cases. The overall response rate was 55. 6%, and the response rate in 16 cases given bevacizumab as first-line was 56. 3%. The response rate in 3 cases whose CEA was within the normal range before chemotherapy was 100%. However, the response rate in 15 cases whose CEA was over the normal range was 46. 7%. Furthermore, 6 cases among 7 whose CEA was over 100 ng/mL had 5 months or less during which CEA could be kept under control with a mean period of 3. 0 months. On the contrary, 6 cases among 8 whose CEA was under 100 ng/mL had 5 months or more of CEA-controlled periods with a mean period of 8. 4 months.

In chemotherapy with bevacizumab, the response rate in patients with normal CEA was higher than that in patients with high CEA. Patients with a CEA level of 100 ng/mL or more had a short CEA-controlled period, suggesting the effect of chemotherapy was small in those patients. There is a possibility that CEA might be clinically useful as a biomarker to predict treatment efficacy in chemotherapy with bevacizumab.