Does the efficiency of bevacizumab treatment depend on the location of the primary tumor?

This study assessed the efficiency of bevacizumab (avastin) treatment in patients with metastatic colorectal cancer. The association between the effectiveness of treatment and the location of the primary tumor was examined.

Colorectal cancer can originate from different sections of the large intestines. The origin of the cancer is referred to as the primary tumor location. Examples of colon segments that commonly give rise to cancer include the cecum, the ascending colon, transverse colon and descending colon, the sigmoid colon and the rectum. When the cancer has spread from these primary sites to other organs the cancer is referred to as metastatic colorectal cancer.

Bevacizumab is a drug that targets a protein called vascular endothelial growth factor (VEGF), and blocks its function. VEGF is important in the formation of new blood vessel, necessary for cancer growth and spread. Bevacizumab in combination with chemotherapy is currently the standard of care for metastatic colorectal cancer patients.

This study analyzed the medical records of 880 patients. 667 were treated with chemotherapy and bevacizumab, while 213 patients were treated with chemotherapy alone. While the benefit of adding bevacizumab to therapy is already known, this analysis concentrated on the association between tumor location and benefit from treatment.

After 6 years, patients treated with additional bevacizumab and a primary tumor location of the rectum or the sigmoid colon experienced an average progression-free survival (PFS; the time between treatment and until the disease worsens or advances) of 9.3 months and an overall survival of 23.5 months. Patients with a primary tumor location higher up in the intestines (from the cecum and up to the descending colon) experienced an average PFS of 7.2 months and an overall survival of 13.0 months. There was no association between primary tumor location and outcome in patients treated with chemotherapy alone.

In summary, the efficiency of bevacizumab treatment depends on the location of the primary tumor. Adding bevacizumab to chemotherapy is more beneficial for patients with primary tumors originating in the rectum and sigmoid colon.

This study was funded by Roche which manufactures bevacizumab (avastin).

Consult with your physician on the relation between tumor location and recommended treatments.