(Updated with new lede, company, analyst and FDA comments, stock price.)

SEATTLE ( TheStreet) -- Volatility rocked Dendreon ( DNDN) shares Tuesday morning after an independent and unconfirmed research report claimed that the U.S. Food and Drug Administration was going to convene an advisory panel meeting to review the company's prostate cancer drug Provenge.

Dendreon shares fell about 10% to below $30 a share in pre-market trading as copies of the bearish report from Favus Institutional Research hit Wall Street's trading desks.

Dendreon quickly countered, insisting that FDA told the company an advisory panel for Provenge would not be scheduled. The rebuttal helped Dendreon shares recover, pushing the stock up $2, or 6%, to $34.57 in recent trading.

The FDA is expected to issue an approval decision on Provenge on or before May 1. The deadline for FDA notifying Dendreon about the need for an advisory panel meeting has already passed, which is why the Favus report issued Tuesday morning spooked investors.

"We have been in contact with physicians who have been invited by the FDA to participate in an upcoming FDA Advisory Committee Panel Meeting to discuss Provenge," said Elliot Favus of Favus Institutional Research in a note sent to institutional investor clients Tuesday morning.

Favus' claim remained unanswered for some time, until Dendreon spokeswoman Katherine Stueland later countered that, "We have received no indication from FDA that we should be preparing for an advisory panel meeting."

Two FDA spokespersons confirmed that there will be no advisory panel meeting for Provenge, according to CNBC reporter Mike Huckman, writing via Twiter.

"I think he's wrong, but even if he is right the panel voted positively last time. The data are stronger this time so I would expect another positive vote and the FDA to approve the drug so that prostate cancer patients can finally have access to this lifesaving drug," said David Miller of Biotech Stock Research, an independent biotech investment newsletter and a long-time follower of Dendreon.

Miller added that Dendreon's management, only last week, said FDA had not been in contact with the company about scheduling an advisory panel for Provenge.

Deutsche Bank biotech analyst Mark Schoenebaum also defended Dendreon this morning. "In my opinion, if a panel is called by FDA, Dendreon's stock could be down 10-20% as most didn't expect a panel. However, given the good Provenge survival data, my sense is that it will pass any such panel, as it passed the 2007 panel with even weaker data. So even with a panel, I think approval is likely by year-end 2010."

In his report, which he calls a "reason to sell" Dendreon, Favus writes, "We believe that the Street is not expecting an FDA Panel to discuss Provenge and that the announcement of an FDA Panel to discuss Provenge will put significant downward pressure on DNDN shares."

-- Reported by Adam Feuerstein in Boston.

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