The Food and Drug Administration says the world's best-selling cancer drug is ineffective against treating breast cancer, dealing a major blow as its manufacturer attempts to keep the drug on store shelves.

The FDA recently concluded Avastin doesn't extend or improve the lives of breast cancer patients.
    
Swiss drug maker Roche is now challenging the government, ask the FDA for more time to study if patients with certain genetic proteins respond better to the drug.

Avastin is approved for advanced breast cancer that has spread, or metastasized, to other parts of the body -- which is considered incurable.

Avastin supporters say patients need every option available, despite the side effects.

"There seems to be this perception that there are all these kinder, gentler treatments for metastatic breast cancer, but I'm not aware of those treatments, said Dr. Kimberly Blackwell of the Duke Cancer Institute.

Avastin is still approved for treating colon, lung, kidney and brain cancer, which the FDA is not challenging.