Avastin. - 
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Jeremy Hobson: Now to a high stakes hearing that the Food and Drug Administration is holding today. It's about whether the drug company Roche can continue to market its drug Avastin to treat breast cancer. The company got preliminary approval a few years ago. But last December, the FDA considered undoing that. Today Roche will make its case in the first challenge to the FDA's conditional approval process.

From our Health Desk at WHYY in Philadelphia, Gregory Warner reports.

Gregory Warner: The so-called accelerated approval program at the FDA first came out of the debate over access to experimental drugs for HIV/AIDS. The idea was the agency should move quickly to grant approval for drugs where lives were at stake -- even before all the evidence was in.

Karuna Jaggar: The whole point of a provisional approval is that it can be rolled back, if it turns out the drug does not perform as first expected.

Karuna Jaggar of the advocacy group Breast Cancer Action says that the FDA did just that. It provisionally approved the drug Avastin for late stage breast cancer in 2008. But the agency rolled it back when later tests showed the drug did not increase overall survival and had potentially fatal side effects.

Roche makes $1 billion a year from Avastin's use in breast cancer. It appealed the FDA decision. And patients' families called their representatives in support of the drug. Harvard professor Daniel Carpenter says all that political pressure has many scientists worried.

Daniel Carpenter: People are worried that once you grant provisional approval, it's increasingly difficult, if not impossible, to reverse.

He says that if the FDA loses this fight, it may make it harder for future drugs to get accelerated approval in the first place.

In Philadelphia, I'm Gregory Warner for Marketplace.

Follow Gregory Warner at @radiogrego