OS is not the "gold standard" it was the only option left to nwbo
Firstly, when the trial was established in 2007, the primary ‘end point’ (the individual result) that the trial wanted to assess was whether adding DCVax-L to the standard of care would extend what is known as progression-free survival (the time until patients’ disease progressed and grew significantly).
However, it was later discovered that many patients experience something called ‘pseudo-progression’, whereby the body’s immune response make it look like the tumor has grown significantly – and imaging techniques can not sufficiently distinguish between the immune response and tumor growth.
It was therefore not possible to establish the impact of the vaccine on progression-free survival, and so the end-point of the trial was changed to overall survival (how long patients lived in total).
Secondly, the trial was established as a ‘crossover’ placebo-controlled trial, which meant that the patients who were initially randomized to the placebo group eventually then ‘crossed over’ to receive DCVax-L at the point their glioblastoma recurred – as it would be unethical for patients to undergo such an invasive procedure to extract immune cells from the blood for no potential benefit.
This meant that, when assessing the effect of the vaccine on overall survival in the trial, there was no longer a control group who had received a placebo to compare against – as there would traditionally be in randomized control trials.
The researchers therefore compared the results in those receiving DCVax-L to the survival of those in an ‘external control group’, selected from 15 parallel trials being run at similar institutions, who had received the same current standard of care.
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