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Predicting the Effectiveness of Avastin

Monday, September 21, 2009 at 06:10 PM EDT

A couple months ago, the FDA approved Avastin for use in treating brain cancer. The new approval is just the latest in a growing number of applications for the drug. First approved in 2004 to fight colorectal cancer, Avastin is now considered an avenue of treatment for lung, breast and other forms of cancer.

However, the effectiveness of Avastin is highly variable on a case-by-case basis. While some patients experience a considerable increase in survival time thanks to the drug, Avastin only delivers a 2-month increase in expected overall survival when compared to other drug treatments.

Initially heralded as a breakthrough drug, doctors are now coming to realize a vast set of complexities behind the effectiveness of Avastin.

Avastin works by blocking a cancer’s ability to feed a growing tumor with new blood vessels. This is accomplished by inhibiting the function of a vascular endothelial growth factor (VEGF) protein that is responsible for stimulating formation of new blood vessels.

When successful, Avastin deprives a tumor of oxygen, limiting or reversing growth. However, for too many patients, the drug has no effect at all.

The variability of success is based on genetic variations present in a patient. Unfortunately, the responsible DNA has yet to be identified.

In absence of more targeted answers, doctors continue to dole out Avastin to a high number of cancer patients in the hopes that they will respond positively. However, a relatively low number of patients are favorably affected by the treatment. Add in the high cost of the drug (up to $55,000 for a single treatment), and doctors are clamoring to create a more focused means of identifying viable patients for the drug.

To achieve this, researchers at Genentech (Avastin’s manufacturer) have already sifted through 150 genetic markers in the hopes of identifying pertinent genes. The Susan G. Koman for the Cure advocacy group has also set aside $6 million to research the subject over the next five years. Hopefully, these considerable efforts will lead to genetic discoveries that doctors can use to predict the effectiveness of Avastin in future patients.