UPDATE 4-US FDA staff question Roche drug breast cancer data

* Two studies fail to confirm earlier Avastin results

* Roche drops 4 percent in Swiss trading

* Advisory panel to weigh data on Tuesday

* Marketing restrictions could depress sales (Adds closing shares, additional Roche comment, details on drug’s effectiveness, side effects, price)

By Lisa Richwine

WASHINGTON, July 16 (Reuters) - The benefits of Roche AG's ROG.VX Avastin may not outweigh the risks for patients with advanced breast cancer, U.S. reviewers said on Friday, knocking the Swiss company's stock down 4 percent on fears that regulators could restrict marketing of the blockbuster drug.

Two studies of Avastin, Roche’s top-selling drug, failed to show the level of benefit for advanced breast cancer patients seen in an earlier trial. A Food and Drug Administration advisory panel will review the Avastin data on Tuesday.

Investors are watching to see if the FDA might revoke Avastin’s approval for breast cancer.

If that happens, the company could no longer promote the drug for that disease. Doctors could still prescribe it for that use as it would remain on the market with approval for other cancers, but sales could fall.

“There is a significant probability the breast cancer indication is withdrawn” in the United States, Berenberg Bank analysts said in a research note. Other analysts said they thought the advisory panel would back the breast cancer use.

About $1.2 billion of Avastin’s projected $6.5 billion in sales this year will come from breast cancer use worldwide, Sanford Bernstein analysts estimated.

Avastin won clearance for breast cancer in 2008 under a shorter approval process, but Roche was required to run two follow-up studies to confirm the drug’s effectiveness and receive full approval.

Those studies “failed to confirm the magnitude of (progression-free survival) improvement” seen in the initial breast cancer trial, the FDA staff said.

Progression-free survival is the time patients live without their cancer getting worse. Avastin, which is given intravenously, extended that time period by 5.5 months in the intial study. In the two later studies, the time ranged from about one month to nearly three months.

The level of improvement for the latter studies was “not clinically meaningful,” the FDA reviewers said, adding that the “risk-benefit ratio” of Avastin plus chemotherapy “may not be considered favorable.” The known risks include gastrointestinal perforations, bleeding and blood clots.

The agency wants input from the advisory panel on “whether clinical benefit has been demonstrated,” the summary said.

Avastin did not extend patients’ overall survival in any of the studies.

Kepler Capital Markets analyst Martin Voegtli said the study results were not new and that he expected most panelists to support full approval of Avastin as a first-choice treatment for advanced breast cancer.

“The reaction in the Roche stock is overdone,” Voegtli said. FDA documents for advisory panels “tend to focus more on the negative aspects, so I am not worrying about this too much at this point.”

The FDA usually follows panel recommendations. A final FDA ruling is due by Sept. 17.

Helvea analyst Karl-Heinz Koch also said he expected a positive outcome. He said did not think the FDA would withdraw the approval after doctors had been using the drug to treat breast cancer for several years.

Roche said its research supported Avastin, known generically as bevacizumab, in advanced breast cancer. The company is asking the FDA to expand the approval to include use with other types of chemotherapy.

Dr. Philippe Bishop, a Roche vice president, said the rate of serious complications was low and the extended time without cancer growing was meaningful for patients with advanced breast cancer. At that stage the disease cannot be cured and the goal is to stablize patients as much as possible, he said.

“Avastin is helpful for patients with metastatic breast cancer,” he said in an interview. “We remain convinced Avastin should be a choice in this setting.”

The drug’s wholesale cost is about $8,000 per month for advanced breast cancer. Roche limits the annual cost for any FDA-approved use to about $57,000.

Roche stock lost 4.2 percent in Swiss trading after the FDA review was released. (Reporting by Lisa Richwine; Additional reporting by Katie Reid in Zurich; Editing by Lisa Von Ahn, Leslie Gevirtz)