Study of Roflumilast in Combination With Standard Chemotherapy for High-risk Diffuse Large B-cell Lymphoma

All patients will receive R-CHOP therapy at standard doses according to the standard preparation and infusion procedures of each investigational site, which is to be repeated every 21 days for a total of 6 cycles. All patients will receive a fixed oral dose of one 500 microgram (μg) tablet per day with or without food for all 21 days of each cycle, which will amount to a total of 126 doses of roflumilast.