Immunochemotherapy With Rituximab and Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone Significantly Improves Response and Time to Treatment Failure, But Not Long-Term Outcome in Patients With Previously Untreated Mantle Cell Lymphoma: Results of a Prospective Randomized Trial of the German Low Grade Lymphoma Study Group (GLSG) | Synapse