office 2016 click to run folder size recduce

I get every few days a new sub-folder in microsoft ClickToRun folder C:\ProgramData\Microsoft\ClickToRun. I have the office 2016 preview. each sub folder has hundreds of files like this one:

A796A3A0-C534-4C16-B12A-5B95B6F05D8B.stream.x64.x-none.1028069089

It's now about 11 GB of my hard drive. Can I erase the old ones? why is it growing so big?