AstraZeneca ( AZN) has seemingly done the impossible. In a dramatic, and somewhat stunning comeback, an advisory panel of the Food and Drug Administration voted Tuesday to recommend approval for the drugmaker's experimental cancer drug, Iressa, as a new treatment for patients with advanced lung cancer. The positive recommendation from the panel of cancer experts, on an 11-3 vote, came one day after FDA staff reviewers raised serious questions about the credibility of the clinical studies designed to test the drug. But in a confusing twist to the meeting, the panel members also agreed, by a 9-5 vote, with the FDA's assertion that AstraZeneca should be required to conduct a more rigorous, controlled study to verify Iressa's clinical benefit. In some ways, the two votes seemed to contradict each other, which could give the full FDA fits as it tries to make sense of the panel's recommendations and render a final decision on the drug. Investors were clearly focused on the bright side, however. AstraZeneca shares, down all day, soared as news of the vote broke late in the day. The stock closed the day up 4% to $30.70. Bernstein analyst Catherine Arnold, who had predicted a negative outcome for Iressa at the panel meeting, said that while there was one negative and one positive vote on Iressa, the positive vote likely would be more influential with the FDA. Arnold rates AstraZeneca market perform, and her firm doesn't have a banking relationship with the company. The focus of Tuesday's meeting of the Oncologic Drugs Advisory Committee was to discuss the merits of Iressa as a treatment for lung cancer patients who had failed two previous courses of chemotherapy. In other words, Iressa would be a new treatment for patients who had run out of all other medical options. Last May, AstraZeneca released test results that showed Iressa was effective in shrinking tumors in just under 11% of these patients, while 36% of patients showed an improvement in their lung cancer symptoms, such as the ability to breath easier. From the start, the panel members seemed to agree with FDA assertions that these positive results were rather suspect because AstraZeneca did not perform controlled studies to test Iressa against a placebo. While panel members concurred that Iressa seemed to have some positive effect against tumors, they found it impossible to truly measure that effect, especially when it came to determining whether the drug improved patients' quality of life. This led to the panel's first vote, 9-5, calling on AstraZeneca to conduct a randomized, controlled study of Iressa, in order to bolster proof of the drug's efficacy. At this point, it looked bad for AstraZeneca. But then, a dramatic turnaround. The panel was asked by FDA officials if Iressa should still be granted an accelerated approval, based on the belief that the 10% response rate in these advanced lung cancer patients was a good predictor of future clinical benefit for patients. Richard Pazdur, the head of the FDA's cancer drug division, said this would be the crucial panel vote. By an 11-3 vote, panel members said yes. By voting to recommend Iressa, the panel decided, in some respects, to overlook disappointing results in two subsequent Iressa clinical trials, known as the INTACT studies. These studies showed that Iressa, when given with standard chemotherapy, failed to improve the survival rate of patients with less-advanced lung cancer. AstraZeneca has been unable to explain these poor results, a fact that clearly bothered FDA officials at the advisory committee meeting. But panel members seemed less bothered by it. Instead, they were swayed in Iressa's favor by the fact that the drug is safe -- it doesn't cause any of the nasty side-effects of chemotherapy -- and that some terminally ill patients were clearly helped. This latter point was brought home in very human terms by a parade of lung cancer patients who sang Iressa's praises during the public hearing portion of the advisory panel meeting. Many of these people told panel members that they would not be alive today if it wasn't for Iressa. These patients -- all of whom took Iressa through a compassionate use program -- seemed to be the wild card that really helped AstraZeneca in the end. The company has allowed more than 18,000 patients access to Iressa outside its clinical trials, creating a very vocal and persuasive lobbying voice in the drug's favor. It still remains to be seen just how the FDA reconciles the two votes in reaching a final decision on Iressa. There was a lot of discussion at the meeting about how to design a new, controlled clinical trial of the drug. AstraZeneca officials said they were willing to conduct such a study, in theory, but still needed to consult with doctors and the FDA on a specific trial design. But investors, it seems, were overjoyed to finally have some bright news from the experimental class of targeted cancer drugs like Iressa, bidding up rival companies that are working on similar drugs. OSI Pharmaceuticals ( OSIP) closed Tuesday up 28% to $16.73; ImClone Systems ( IMCL) was up 32% to $8.07; Abgenix ( ABGX) rose 17% to $6.81 and Genentech ( DNA) was up 4% to $30.19.