According to the results of a Phase III clinical trial presented at the 2009 annual meeting of the American Society of Clinical Oncology (ASCO), addition of the targeted therapy Avastin® (bevacizumab) to post-surgery chemotherapy does not improve disease-free survival among patients with early-stage colon cancer. These results were previously made available in a press release from Roche.
Targeted therapies are anticancer drugs that interfere with specific pathways involved in cancer cell growth or survival. Some targeted therapies block growth signals from reaching cancer cells; others reduce the blood supply to cancer cells; and still others stimulate the immune system to recognize and attack the cancer cell. Depending on the specific “target,” targeted therapies may slow cancer cell growth or increase cancer cell death. Targeted therapies may be used in combination with other cancer treatments such as conventional chemotherapy.
Avastin is a targeted therapy that blocks a protein known as VEGF. VEGF plays a key role in the development of new blood vessels. By blocking VEGF, Avastin deprives the cancer of nutrients and oxygen and inhibits its growth. Avastin’s effects on blood vessels may also improve the delivery of chemotherapy to the tumor.
Currently, Avastin is approved for the treatment of selected patients with advanced colorectal, breast, or non–small cell lung cancer. Given the benefit of Avastin in metastatic colorectal cancer, researchers have also initiated studies to evaluate Avastin in the adjuvant (post-surgery) treatment of patients with earlier-stage colon cancer.
The current results are from a Phase III clinical trial known as NSABP C-08. The study enrolled 2,710 patients with Stage II or Stage III colon cancer. After surgical removal of the cancer, patients were assigned to receive six months of chemotherapy alone (mFOLFOX6) or six months of chemotherapy plus Avastin followed by an additional six months of Avastin alone after chemotherapy had ended.
After a median of three years of follow-up, 77.4% of patients treated with chemotherapy plus Avastin were alive and free of disease compared with 75.5% of patients treated with chemotherapy alone. The difference between study groups did not meet the criteria for statistical significance, suggesting that it could have occurred by chance alone.
Interestingly, however, the Avastin group did experience better disease-free survival during the first year of the study (the year during which they received Avastin). In a prepared statement, one of the researchers noted: “Our overall conclusion is that [Avastin] was not effective as an adjuvant treatment for early-stage colon cancer, but the transient benefit we saw in patients who received [Avastin] illustrates that we have more to learn about how this reagent works, and we need to design more clinical trials to determine how it can be used most effectively.”
Reference: Wolmark N, Yothers G, O’Connell MJ et al. A phase III trial comparing mFolfox6 to mFolfox6 plus bevacizumab in stage II or III carcinoma of the colon: Results of NSABP protocol C-08. Presented at the 2009 annual meeting of the American Society of Clinical Oncology, May 29-June 2, 2009, Orlando, FL. Abstract LBA4.