The Chicago Sun-Times reports on their web-site
Robert Novak has announced his immediate retirement following the diagnosis of a brain tumor, a prognosis the Sun-Times' political columnist describes as "dire."
Link here
As noted when news broke that he had a brain tumor, noone would wish this on anyone. In the earlier news it was suggested that Novak was taking a leave of absence. This is the first that I see here that he's retiring.
I searched for an earlier posting, will delete and/or update soon