Predicting response to bevacizumab treatment

This study evaluated whether past surgery could be used to predict response to bevacizumab (Avastin) treatment among metastatic cancer patients.

Combined treatment with bevacizumab and chemotherapy is the standard of care for the treatment of metastatic (wide spread) colorectal cancer. Bevacizumab acts by inhibiting formation of new blood vessels vital for cancer growth and spread. While several studies have demonstrated a significant benefit to survival with bevacizumab treatment, not all patients treated respond to therapy, and benefit from treatment varies widely. To date, no markers have been found that may be used to predict response to bevacizumab.

This study assessed whether the presence of the primary (original) colorectal tumor influenced survival among patients receiving bevacizumab. The records of 409 metastatic colorectal cancer patients were analyzed. 333 (81.5%) of the patients previously underwent surgical resection of the primary tumor, while among the 76 (18.5%) remaining patients the primary tumor was still present during treatment.

Results revealed that bevacizumab did not influence survival among patients bearing a primary colorectal tumor. By contrast, among patients who previously underwent primary tumor resection, addition of bevacizumab to chemotherapy reduced the risk of mortality by 29% compared to chemotherapy alone.

This study concluded that the addition of bevacizumab to chemotherapy is associated with improved survival only for patients not bearing the primary colorectal tumor.