May be you can try using a Sub Report and the Sub report can have total count of all pending cases.

In summary view we have this feature using Trend but how will i achieve this in report definition?

You can use a function alias with a case statement to lump them and aggregate possibly.  Pending = case when status like 'Pending%' then 1 else 0 end. That would evaluate for each record and could be summed in the report def. Issue there would be performance due to table scans. Alternatively, you could create a declarative property for StatusCategory or something similar and when your status field changes, it could record "New", "Open", "Pending", "Resolved", etc. into that field. Expose & index that field then it would work faster.