A slim majority - 5 to 4 - believe the Genentech med shouldn’t be approved for patients with breast cancer that has spread to other parts of the body, because the drug’s benefit in slowing tumor growth isn’t worth the added risk of serious side effects, including high blood pressure and death. The move rattled investors, who sent Genentech shares plunging.

“Everybody wants to offer metastatic breast cancer patients hope, but we shouldn’t offer them false hope,” says Natalie Compagni-Portis, a panel member and a patient representative with Breast Cancer Action, an advocacy group, Bloomberg News reports. “We have to raise the bar in terms of safety.”

Prior to the meeting, FDA medical reviewers noted that Avastin slowed the progression of cancer, but failed to improve patient lifespans. And they questioned whether the drug should be approved for the new use, considering toxicity issues and side effects. The clinical trial supporting expanded use found Avastin slowed the spread of tumors for an extra 5.5 months when used with chemotherapy, compared with patients given chemotherapy alone. But patients on the drug had a 20 percent increase in serious side effects - six of the 363 patients, or 1.7 percent, who took Avastin died from side effects, compared with none of the 348 patients on chemotherapy.

“These patients are terminal, and it’s our job to make their lives better, not to say that it’s OK to have a stroke or that it’s manageable,” said Maha Hussain, an oncologist at the University of Michigan and the advisory panel’s chairwoman, during the meeting in Gaithersburg, Maryland. “You didn’t show that patients are living better or that they’re living longer.” She added that data presented to the panel included too many cases in which radiologists had differing interpretations of whether a patient’s cancer had spread.

The advisory panel was asked to consider whether it’is valid to approve a drug that failed to extend lives, although it showed a capacity to slow tumors. The FDA sometimes approves cancer drugs on what are known as surrogate markers, such as slowing the spread of tumors, instead of waiting for survival data that can take years to collect.

Slowing tumors improves quality of life for patients, and that is enough to support approval, said Eric Winer, an oncologist at Dana-Farber Cancer Institute in Boston, who spoke to the panel during Genentech’s presentation. Winer didn’t receive compensation from the company to travel to the meeting, he said.

“The bottom line is the day-to-day toxicity for most patients in the clinical trial, and in clinical experience, is quite limited,” Winer said. “I wouldn’t be here today if I didn’t think it should be a treatment option for women.”

Avastin was the first med to cut off blood supply to malignancies, is approved for treating colorectal cancer and lung cancer. With nearly $1.7 billion in US sales through September, Wall Street believed the new indication could add $1.3 billion in 2009, Bloomberg writes. Roche, Genentech’s largest shareholder, markets Avastin outside the US.

The negative panel vote Wednesday is the second FDA-related setback for Avastin as a breast cancer therapy, the Associated Press reminds us. Last September, FDA asked the company to resubmit medical scans showing cancer progression in patients. The agency is scheduled to make its final decision on Avastin in February. Analysts said the panel’s decision will have implications for all drug makers working on cancer therapies, because companies will increasingly have to show overall survival improvement to gain US approval, rather than just delayed cancer progression, the AP adds.