A Food and Drug Administration panel took a major step Wednesday toward ending use of the best-selling drug Avastin for treating advanced breast cancer in the United States, despite appeals from distraught patients and the company manufacturing the drug.

A crucial six-member FDA advisory committee unanimously concluded that the drug was harming women more than it was helping them. FDA Commissioner Margaret A. Hamburg must make a final decision, but agency commissioners usually follow advisory panel recommendations.

The fate of the drug for breast cancer has been closely watched by patients, oncologists, women’s health advocates, health-care policymakers, politicians and the pharmaceutical industry. The case has triggered strong reactions from advocates of easier access to new treatments and from critics fearing health-care rationing. It is also being seen as one of the most visible medical examples of scientific evidence winning out over an animated public outcry. Ultimately, clinical trials failed to support the drug’s early promise for breast cancer treatment.

“I think we all wanted Avastin to succeed, but the reality is that these studies did not bear out that hope,” said Natalie Compagni Portis, who represented patients on the panel.

If the FDA revokes Avastin’s approval for treatment of breast cancer, the drug would remain available for other cancers, enabling doctors to prescribe it “off-label” for breast cancer patients. But the decision would probably prompt insurers to stop paying for the drug — which costs about $88,000 a year per patient — for breast cancer treatment. . Breast cancer patients also would lose eligibility for a program sponsored by the drugmaker, Genentech, that caps the annual cost at about $57,000 for women making less than $100,000 a year.

“A terrible tragedy has occurred,” said Frank Burroughs of the Abigail Alliance for Better Access to Developmental Drugs, which is among the groups that has been pressing the FDA to maintain Avastin’s approval on the grounds that it benefits some patients.

But the decision was praised by others, including several leading breast cancer advocacy groups and experts who said it was important for the agency to base its decisions on the scientific evidence, not emotional appeals, especially when lives are at stake and controlling health-care costs is so crucial to the nation’s economy.

“Now we must focus attention and resources on drugs that will truly make a difference for women suffering from breast cancer. Avastin does not,” said Fran Visco of the National Breast Cancer Coalition.

“I think it’s great that they are willing to make a tough call,” said H. Gilbert Welch of the Dartmouth Institute for Health Policy and Clinical Practice.

The FDA is not supposed to acknowledge cost in drug approvals, and officials have stressed that the price was irrelevant. But coming amid a continuing national debate over President Obama’s health-care overhaul, the fight about Avastin has become entangled in the politically sensitive struggle over medical spending and effectiveness.

Avastin is among the costliest of a new generation of anti-cancer medications that appear to give patients a few extra months of life. It was the first drug designed to fight cancer using a new strategy — inhibiting blood flow to tumors — and was approved for treating several malignancies.

Its 2008 approval for breast cancer was controversial from the start. Only one study had found that the drug appeared to slow the growth of an advanced breast tumor, delaying progression by about 5 1 / 2 months. It remained unclear whether patients lived longer or enjoyed a better quality of life. So the FDA authorized Avastin under a special program designed to make advances in treatment available to patients quickly. The deal was that Genentech must validate the risk-benefit ratio with additional studies.

The agency moved in December to revoke the approval based on a July 20 advisory committee conclusion that the new studies had not shown that the drug extends life and had indicated that it slowed tumor growth for far less time — perhaps as little as a month.

Genentech immediately challenged that decision. The FDA’s two-day meeting that ended Wednesday was marked by unusually tense exchanges between representatives of Genentech and agency officials. They clashed repeatedly over issues including the interpretation of studies evaluating Avastin and whether the agency had shifted its criteria for approving the drug.

“We are very disappointed by the committee’s recommendation,” Hal Barron, Genentech’s chief medical officer, said in a statement afterward. “We remain ready to collaborate with the FDA to find a solution that is in the best interest of patients who need Avastin.”

The committee’s recommendations, which prompted shouts of protest from some in the audience, came after Genentech asked the agency to keep the authorization for breast cancer while the company conducts another study to confirm the drug’s benefits.

Dozens of protesters, many wearing pink T-shirts and carrying signs that included “Save Avastin” and “I question the FDA’s right to take life from a woman,” demonstrated outside the agency’s Silver Spring headquarters as the hearing began Tuesday, accusing budget-conscious government bureaucrats of rationing care by getting between patients and life-saving drugs. The committee then heard several hours of often-emotional pleas from patients and family members who believed the drug was keeping them or their loved ones alive, as well as from advocates for patients suffering from other cancers worried about the impact on their treatment. The benefits of the drug have been shown to outweigh the risk for other cancers.

“The FDA has stubbornly put itself between patients and their doctors by severely limiting access to a life-extending drug, and has even cited cost as a criterion,” Sen. David Vitter (R-La.) said in a statement after Wednesday’s vote.

FDA officials gave a series of detailed scientific presentations to bolster their argument that the existing data indicated that Avastin provided little or no benefit and put women at risk for potentially life-threatening complications, including high blood pressure, hemorrhages and heart attacks.

Before the FDA announced plans to revoke Avastin’s approval for breast cancer in December, the drug was being prescribed annually to about 17,500 U.S women with breast cancer. Globally, Avastin had annual sales of $6.8 billion in 2010, making it the world’s best-selling cancer drug and top-selling product for Genentech and Roche, its Swiss owner. Genentech has waged an unprecedented campaign to save U.S. approval of the drug, which alone brings in nearly $1 billion a year.