CHICAGO (AP) - Conservative political commentator Robert Novak says he's lost partial vision and undergone a lengthy surgery to remove a tumor since being diagnosed with brain cancer.

Novak writes in a column Saturday on the Chicago Sun-Times' Web site that his "brain tumor brings out the best in people." He says he underwent a four-hour surgery Aug. 15 to remove a 3-by-1½-inch tumor, and says he still must undergo radiation and chemotherapy treatment.

The 77-year-old Novak announced his retirement on August 4th, less than a week after he struck a pedestrian with his car in downtown Washington.

He is perhaps best known as the longtime co-host of CNN's "Crossfire" from 1980 to 2005.