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FDA Approves Vaccine For Prostate Cancer
reverseengineer writes "The US Food and Drug Administration has given its first first approval for a therapeutic cancer vaccine. In a clinical trial 'involving 512 men, those who got Provenge (sipuleucel-T) had a median survival of 25.8 months after treatment, while those who got a placebo lived a median of 21.7 months. After three years, 32 percent of those who got Provenge were alive, compared with 23 percent of those who got the placebo. ... "The big story here is that this is the first proof of principle and proof that immunotherapy works in general in cancer, which I think is a huge observation," said Dr. Philip Kantoff, chief of solid tumor oncology at the Dana-Farber Cancer Institute in Boston and the lead investigator in Dendreon's largest clinical trial for the drug. "I think this is a very big thing and will lead to a lot more enthusiasm for the approach."'"
According to my calculation, if the null hypothesis were true (i.e. the vaccine were just a placebo) there would be about a 1 in a million chance of a result this extreme (4.85 standard deviations above the mean). So it is highly significant statistically speaking. Whether it is clinically significant or not is a different question, of course.
That's not what he meant, and this isn't the same context and you know it.
SHAME on you for trying to pollute political discourse.
The Kruger Dunning explains most post on
Several major points:
1. There were 512 people in the trial. Assuming that these were split into two groups, that n=256. Of course it depends on the standard deviation, but you could get your p value very low with an n like that.
2. Human trials of drugs that treat potentially fatal conditions are generally only allowed for patients who've failed "best available" therapy at least once, because it would be unethical to deny standard therapy to someone in a trial. The relative risk reduction may get better when used outside the context of the trial because of that. Or not. Remains to be seen, as usual.
3. As our understanding of the immune system and the molecular processes underlying cancer improves, we will slowly unravel a huge potential for case-by-case-based treatment of cancer. As a matter of fact, I believe a recent study I am too lazy to look up to link has shown that people whose cancer therapies relied on analyzing the biochemistry of each individual tumor resulted in about a 50% increase in 5-year survival, compared to conventional pathology-based treatments. The future is bright for oncology.
4. The caveat of #3 is that such treatments are expensive, and will get progressively more expensive based on the degree of testing and individualization required (until the wide use and technology make them cheaper of course). This will necessarily introduce a further divide into the available treatments for the rich and the poor, and contribute to the class struggle that's already rather inflamed. The problem is that there's no OTHER way - giving everyone $100'000 treatments would bankrupt us rather quickly. Instead, similar to the case with electronics, we will simply have to suffer through the period of expensive first-adopter treatments, until the improvements in laboratory techniques and high-throughput testing make such treatments increasingly affordable.
If you assume each person has (independently) a 0.23 probability to survive 5 years, then the overall distribution must be binomial with standard deviation sqrt(n*p*(1-p)).
Is it just me or do those numbers look too close to be statistically significant?
The summary mentions a sample size of 512. The standard error of the mean decreases by the square root of the sample size. For 95 % certainty, if the standard deviation of their measured data is less than (32 percentage points - 23 percentage points)*sqrt(512)/1.96 = 104 "percentage points", which is quite likely, (see a tutorial), then you *can* say that this is statistically significant.
If you want some real details and not my back of the envelope calculations of dubious quality, you can see the actual slides [PDF], which does have details on the statistical significance of the results.
Long story short, they're significant at the level tested (95 %, generally good enough for these kinds of studies).
>> Standing on head makes smile of frown, but rest of face also upside down.
Actually I am wrong.
As some people have pointed out below, the sample who received the vaccine was only of size 256, not 512. So the p value is not 1/1000000 but more like 3x10^-4. Still significant, but not what I said before. Sorry.
Bright indeed. The immune system has an amazing ability for specificity. Once we master the art of training the immune system to recognize and kill cancer cells the fight will be over. Interestingly, there was a cancer treatment in the late 1800's that relied on injecting cancer tumors with an infectious serum designed to elicit an immune response. The treatment had some success but was dangerous as the patient ran the risk of death from infection. I really think immuno therapy is the future of cancer therapy.
To be honest I find that unlikely. Unfortunately there is a reason why that cancer spread - it has already managed to evade the immune system.
Immune therapy is but one of the treatments that become available once you understand tumor biology. Even more promising are drugs that can have direct effects on the multiple pathways that have been disrupted or bypassed by the cells on their way to becoming cancerous. As we gain more complete understanding of these molecular mechanisms, as well as enhance our ability to identify the mutations or dysfunctions in each individual tumor, we'll be able to target them efficiently. For instance, we may be able to fix the "suicide" pathways (yes, I know it's called apoptosis) that were necessarily disabled in a particular tumor, and by treating the problem cause the tumor cells to destroy themselves and they were programmed to do by evolution.
But further down this thread there's a study showing the opposite for those under 40. http://www.sciencedaily.com/releases/2009/01/090126082343.htm
There was never a time in written history when we all died at 40 or so. The average lifespan figure was strongly skewed by a high infant mortality.
While cancer becomes more common in old age, it is hardly a disease of old age. Children get it, young adults get it, middle aged people get it and old people get it. Most notably for your argument, it happens all too often before age 40.