Prostate cancer vaccine said to 'significantly' prolong survival

A controversial prostate cancer vaccine produced by Dendreon Corp. of Seattle "significantly" improves survival of patients, the company said Tuesday morning without releasing further details of the trial. The trial was designed to detect a minimum 22% increase in survival and experts speculate that it did at least that well. Further results of the trial will be released April 28 at a meeting of the American Urological Assn. If those findings are upheld, the vaccine, called Provenge, could be the first cancer vaccine approved by the Food and Drug Administration.

Provenge is a so-called therapeutic vaccine designed to treat the disease rather than prevent it from occurring. Physicians collect specialized immune cells called dendritic cells from the patient's blood, mix them with proteins collected from the surface of tumor cells and inject them back into the patient in three doses at two-week intervals.

In an earlier study of the vaccine, the company found that it increased survival of patients with advanced prostate cancer that had spread beyond the prostate by 18 weeks compared to patients given a placebo. After three years, 34% of those in the vaccine group survived, compared to 11% of those in the placebo group. An FDA advisory committee recommended that the agency approve the vaccine for marketing, but the FDA disagreed, arguing that the study did not provide evidence that the vaccine slowed progression of tumors.

That decision provoked outrage among prostate cancer victims and advocates, who argued that the 18-week increase in survival was nearly double the 10-week increase seen with Taxotere, which had been approved. Three congressmen called for a probe of the agency, charging conflicts of interest among some members of the advisory committee.

The new trial in 512 patients was designed to overcome objections to the earlier study. Although few details are available yet, Dr. Eric Small of UC San Francisco told the Associated Press that "this is an exciting result, demonstrating that harnessing a patient's own immune system can successfully attack prostate cancer. Now we have more confidence that the initial results we saw were real."

Prostate cancer is the most common cancer in American men, with an estimated 186,000 new cases diagnosed each year and 28,660 deaths. There are currently no good treatments for disease that has spread beyond the prostate.

-- Thomas H. Maugh II

Comments

[G Arnold]

34% survival means saving millions of lives!!!
I can't get it. Why on earth those disputes are taking place?

[E Michael D Scott]

With all due respect to Mr. Arnold, only about 40,000 or so new patients each year at most are likely to meet the criteria for treatment with Provenge, and on average their survival may be extended for 4-5 months.

To suggest that this implies "millions of lives" being saved is potentially misleading to patients with prostate cancer, the vast majority of whom will not, in any case, die from this disorder, although it will certainly have significant impact on their lives.

Mike Scott
Co-Founder
The "New" Prostate Cancer InfoLink

[The Dude Abides]

With all due respect to Mr. Scott, a 4.5-month median survival benefit does not equate with "on average their survival may be extended for 4-5 months." Median survival compares the survival time of the 50th percentile patient in the Provenge arm (25.9 months in the earlier trial) to the survival time of the 50th percentile patient in the control arm (21.4 months). If one were to calculate "average survival" according to Mr. Scott's misleading definition, then the Provenge arm patients would have had closer to a one-year "average survival" benefit over the control arm patients, seeing as how 34% of them lived for at least three years compared to 11% of the control patients, and according to the March 2007 FDA Advisory Committee briefing documents, roughly 25% of the Provenge arm lived for between 5 1/2 and 7 years as of March 2007.

Approximately 30,000 American men die of advanced prostate cancer every year, and approximately 75-100,000 prostate cancer patients become hormone refractory every year.

Even though the FDA's advisory committee voted 17-0 that Provenge was safe and 13-4 that it demonstrated effectiveness, the most powerful member of that committee (Howard Scher of Memorial Sloan Kettering) started a campaign of influence against approval, all the while sitting on the board of directors of the Proquest Advisors venture capital fund that had tens of millions of dollars invested in Novacea, whose drug Asentar was a direct competitor of Provenge. When Provenge was denied approval due to Scher's pressure, Novacea was able to sign a lucrative partnership deal with Schering Plough, nearly tripling the stock price. Proquest and Dr. Scher were able to cash out with a profit approaching $100 million dollars. Quite a lucrative gig if you can get it, especially when it's okay to commit a felony by not disclosing your conflict of interest with Novacea or Proquest to the FDA when you signed your conflict of interest waiver. Of course, the FDA has stonewalled the Freedom of Information Act request for over 18 months now about how much it knew about Scher's conflicts beforehand.