Peregrine took none of these precautions. Seventy-nine patients were enrolled in the two bavituximab arms but only 40 patients were accounted for in the survival analysis. That means 39 bavituximab patients, or 49%, were censored and excluded from the analysis.
To put Peregrine's 49% patient censoring rate in perspective, six phase III lung cancer studies published recently in the medical literature had an average censoring rate of 19%. On average, each of these studies enrolled 710 patients.
Peregrine's bavituximab study enrolled just 117 patients (including the 38 patients in the control arm) but had more than double the rate of censoring. That speaks to very poor trial conduct.The amount of patient censoring is important but so is the time at which censoring occurs. In well-conducted clinical trials, more censoring occurs after median overall survival is reached. This typically reflects patients who remain alive in the study when the analysis was conducted. If or when these late-censored patients die, the median overall survival estimate of the trial will not change appreciably. Remember, median is the value in the middle, not the average. In the Peregrine study, however, much more patient censoring occurred before median overall survival was reached.
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