Chicago ? Conservative political commentator Robert Novak announced his immediate retirement Monday because of his diagnosis of a malignant brain tumor.

Novak told the editor and publisher of the Chicago Sun-Times that he plans to focus on his treatment and recovery, said Sun-Times spokeswoman Tammy Chase.

Novak told the newspaper his prognosis is “dire,” the Sun-Times reported on its Web site.

“The details are being worked out with the doctors this week, but the tentative plan is for radiation and chemotherapy,” Novak said.