Patients receive calcitriol orally (PO) on days 1, 2, 8, 9, 15 and 16; cisplatin intravenously (IV) over 2 hours on day 2; and gemcitabine hydrochloride IV over 30 minutes on days 2, 9, and 16. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity.