text: Levels of protein in the blood could predict which advanced bowel cancer patients will respond to Genentech/Roche's ($RHHBY) bevacizumab (Avastin), a monoclonal antibody that increases survival in 10% to 15% of patients with the disease. Knowing which patients will benefit from the drug will cut costs by targeting use of the drug more effectively, and will allow those patients who won't improve the opportunity to move on to a more effective treatment more quickly.
  Bevacizumab targets the VEGF-A protein. This protein comes in two forms: VEGF165, which increases cancer blood vessel growth, and VEGF165b, which reduces growth and therefore cuts blood supply to the cancer.
  In a study at the University of Bristol, funded by Cancer Research UK, researchers found that people with lower levels of VEGF165b lived for three months longer than people who had no treatment, but patients with higher levels of VEGF165b had no benefit from bevacizumab, and had similar survival to those who had no treatment. This may be because higher levels of VEGF165b "mop up" the bevacizumab, so less is available to block the blood vessel-promoting version VEGF165.
  According to David Bates of the University of Bristol: "Avastin has shown great potential for a minority of people with bowel cancer, but it's been impossible to predict who will benefit from the drug. Currently, Avastin is not approved by NICE for patients with advanced bowel cancer because they feel that the benefit to an unknown minority of patients does not justify the cost of treatment."
  The next step is to look at larger groups of patients and see whether testing the levels of VEGF165 can identify the patients who will benefit from the drug. In May, we reported on another study that found a potential genetic marker for bevacizumab responders with pancreatic and kidney cancer. Markers like these could open up new markets for Roche and Avastin.