<qa>  How many courses does the treatment repeat every 21 days?Patients receive oral tipifarnib twice daily on days 1-14, gemcitabine IV over 30 minutes on days 1 and 8, and cisplatin IV over 2 hours on day 1. Treatment repeats every 21 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. 