I use Google Earth which used to store huge information in a cache.dat file (800 MB !!) destroyed by error by your CCleaner and this way causing loosing tens hours of navigation to get that information for my offline use !!! Large mistake !!
The keyword "cache" used in many different files handled by various application must not be the only decision key to erase that file !!!
On the other hands, although CCleaner display index.dat files as marked for deletions during its cleaning process, these files are not erased during next system restarting (by the way CCleaner never notifiy on this critical aspect !!!