- Smoking history: current or former cigarette smokers with a history of cigarette smoking of >= 10 pack-years [number of pack years = (number of cigarettes per day / 20) x number of years smoked (eg. 20 cigarettes per day for 10 years, or 10 cigarettes per day for 20 years both equal 10 pack-years)]. Former smokers are defined as those who have stopped smoking for at least 6 months prior to Visit 1. Pipe and/or cigar use cannot be used to calculate pack-year history