What this means is that the system is broken. Right now this figure (20% overall and only 5.9% of industry studies) means that the trials system is giving incorrect results, and billions of dollars are being wasted in the service of industry greed.
This week the media ignored a study looking at that exact question. It was also one of the most important papers to be published this year: only one in five trials on cancer treatment actually gets published; the rest are missing in action. And it gets worse: only 5.9% of industry-sponsored trials on cancer treatment get published. Later, it will get worse again.