Hi reza,
You cannot summerize by recipient in DLP (but you can do it by recipient domain). You can try to use "IT analytics" solution (not sure you will be able to do that) or do it on your own via a CSV export of all your incident and then a processing of this export via excel or any other tool.
I used to do lot of scripting a part of DLP in order to perform some report as DLP by itself does not have a very efficient reporting capabilities even if information are available in the tool.
Regards.