I realized pretty simple atom feed in my application. Sometimes records expire and are no longer published in the feed. Is there a way to remove entry from user`s reader?
If you used GUID/ID* elements in the feed, then posting a blank item with the same GUID as the deleted post will update the post in Google Reader with the blank content.
http://support.google.com/reader/answer/69998?hl=en
Whether any other feed aggregators will update the post ( or even cache the old posts to begin with) is up to them.