A group of long-term Marlboro smokers has filed an action in federal court in New York to force Marlboro maker Philip Morris USA to give them regular low-dose CT scans to catch possible early signs of lung cancer. The action is unusual because it seeks only medical screenings for people whose smoking habit has put them at increased risk of lung cancer, said plaintiffs attorney Jerome H. Block. But past lawsuits seeking medical monitoring for smokers haven't succeeded.