Thursday, May 24, 2012

Septic shock doesn't need my rescue bias

Rescue bias and auxiliary hypothesis bias are tempting distractions when it comes to dealing with data that are counter to our preconceived notions. In general, the role of our cognitive biases in all kinds of discourse, including clinical and scientific, is under appreciated. For this reason I devoted fully two chapters of my book to cognitive biases.

Which makes it even more frightening that, as I read this NEJM paper on the failed drotrecogin PROWESS-SHOCK study, I am still looking for reasons why it failed, other than that just doesn't work. After so many years of trials and tribulations with Xigris, and hopes that this lone therapy ever to have been approved for treating this deadly disease, I am having a hard time letting go.

Yet the rial was meticulous, as all trials designed and overseen by B. Taylor Thompson are -- he is just a brilliant clinical researcher that we all need to learn from. The design considered all the right issues a priori -- multiple interim looks at the data, a possible need to increase the power, heterogeneous treatment effect, and others. Although there were a few numerical imbalances between the treatment and the placebo groups -- blood cultures were positive 4% more frequently and the offending pathogen overall was 5% more likely to be identified in the Xigris than in the placebo group -- I have to accept that these are not the reasons for the observed failure to improve either the 28-day or the 90-day mortality.

I have seen and even blogged about these data before -- the press release had some of them, but, more importantly, Taylor presented them at the Society of Critical Care Medicine meeting back in January. So, this is nothing new. Yet reading all of the details in the pages of the NEJM brings back that pre-conscious cognitive wall that I have to climb over in order to get to reality. And the reality is that the drug just did not work.

But the reality is also that sepsis patients have a better chance of surviving this deadly assault than they did 10 years ago. In the original PROWESS study 28-day mortality in the placebo group was 31%, and these were all kinds of sepsis patients. In the current study, among most severe sepsis patients, those with septic shock, the 28-day mortality was on the order of 25% in both arms -- that's a staggering reduction in this most ill septic population! We really need to appreciate this. In part this trend may be due to some evolution of the disease-host interaction. But in part it has to be because of the concerted effort to understand sepsis better, to study various treatment options, and, most importantly, to implement these learnings at the bedside. In no small part we owe these advances in sepsis care to the short life of drotrecogin alpha.

The data are clearly anticlimactic, and for this reason the current paper has no sex appeal -- just look at the (lack of) press coverage about it. Yet, this is a clear example of countering the traditional publication bias: Here is a manufacturer-funded negative study published in a premier peer-reviewed journal. I realize that it was always a high-profile undertaking, but let's pause for a moment to enjoy this small victory for those who have railed against the spread of biased information in the medical literature.

I don't know if and when another therapy will emerge courageous enough to brave the rough waters of sepsis and septic shock. But one thing is clear: Xigris has served out its purpose, and no amount of rescue bias from me will save it. Rest in peace.    

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1 comment:

  1. I participated in a number of sepsis trials over the years, including Xigris. There are two that stood out as seeming to work, Xigris and Chiron's TFPI, yet each failed to show significance at the end of the day. However, our site's mortality rated dropped from ~40% to <15% -- not because the drugs work, as it turned out, but because all that we learned about taking care of patients with septic shock. As you point out, the "failed" studies still helped a number of our patients and our overall knowledge, so were of considerable value.